# Code Reference β€” Global Glossary _2 pages_ --- # Global Glossary (/docs/global-glossary) # Global Glossary [#global-glossary] Cross-stack interview terms. Browse the sidebar for every cheat sheet in this section. ## Sections [#sections] *All notes are listed in the sidebar.* --- # Global Glossary (/docs/global-glossary/global-glossary) *Cross-stack Β· Interview reference* *** ## πŸ“‹ Overview [#-overview] Alphabetical glossary of **500** terms used across web development, DevOps, databases, testing, security, and system design β€” useful for technical interviews and quick recall. One term, one line. ## πŸ”§ Core concepts [#-core-concepts] | # | Term | Definition | | --- | ----------------------------- | ---------------------------------------------------------------------------------- | | 1 | ACID | Database transaction properties: Atomicity, Consistency, Isolation, Durability. | | 2 | Accessibility (a11y) | Designing UIs usable by keyboard, screen readers, and assistive tech. | | 3 | API | Application Programming Interface β€” contract for programs to talk to each other. | | 4 | API Gateway | Single entry point that routes, auth-checks, and rate-limits backend services. | | 5 | Artifact | Build output (binary, image, package) stored or deployed by CI/CD. | | 6 | Async / Await | Non-blocking style: work pauses until I/O completes without blocking the thread. | | 7 | Authentication | Proving who you are (login, token, certificate). | | 8 | Authorization | What you are allowed to do after identity is known (roles, permissions). | | 9 | BDD | Behavior-Driven Development β€” tests/specs written in human-readable scenarios. | | 10 | Bearer token | HTTP auth scheme: Authorization: Bearer \{token}. | | 11 | Black-box testing | Testing behavior from outside without knowing internal implementation. | | 12 | Blue-green deployment | Two identical envs; traffic switches from old (blue) to new (green). | | 13 | Branch (Git) | Movable pointer to commits; isolates feature work. | | 14 | Cache | Storing data closer to the consumer for faster repeat access. | | 15 | Callback | Function passed to another function to run later on async completion. | | 16 | Canary release | Roll out a change to a small % of users before full promotion. | | 17 | CAP theorem | Distributed systems trade Consistency, Availability, Partition tolerance. | | 18 | CDN | Content Delivery Network β€” edge caches for static assets and sometimes HTML. | | 19 | Certificate (TLS) | Cryptographic document binding a public key to a domain identity. | | 20 | CI/CD | Continuous Integration / Delivery / Deployment β€” automate build, test, ship. | | 21 | Client-side rendering (CSR) | Browser runs JS to render UI after loading a shell page. | | 22 | Closure | Function capturing variables from its surrounding lexical scope. | | 23 | CNI | Container Network Interface β€” standard for wiring containers into networks. | | 24 | Component (React) | Reusable UI unit receiving props and returning elements. | | 25 | Connection pool | Reuses open DB connections instead of opening one per request. | | 26 | Container | Lightweight isolated process with its own filesystem sharing the host kernel. | | 27 | Content-Type | HTTP header declaring body format (e.g. application/json). | | 28 | Context (React) | Share values down the tree without prop drilling at every level. | | 29 | Continuous Delivery | Every change is releasable; prod deploy may be manual or gated. | | 30 | Continuous Deployment | Every passing change auto-deploys to production. | | 31 | Continuous Integration | Merge often; each push runs automated build and tests. | | 32 | Cookie | Small key-value stored by the browser and sent with requests to a domain. | | 33 | CORS | Cross-Origin Resource Sharing β€” browser rules for JS calling another origin. | | 34 | CRUD | Create, Read, Update, Delete β€” basic data operations. | | 35 | CSRF | Cross-Site Request Forgery β€” tricking a logged-in browser into unwanted actions. | | 36 | CSS | Cascading Style Sheets β€” layout, color, typography, and motion for the web. | | 37 | CSS Grid | Two-dimensional CSS layout with explicit rows and columns. | | 38 | CSS Specificity | Rules deciding which selector wins when declarations conflict. | | 39 | Data structure | Organized storage: array, hash map, tree, queue, graph, etc. | | 40 | Deadlock | Tasks wait on each other forever and make no progress. | | 41 | Dependency injection | Supply dependencies from outside instead of hard-coding in a class. | | 42 | Deployment | Putting a built app onto infrastructure users can reach. | | 43 | DevOps | Culture and tooling bridging development and operations. | | 44 | DNS | Domain Name System β€” maps hostnames to IP addresses. | | 45 | DOM | Document Object Model β€” tree representation of HTML the browser scripts. | | 46 | Docker | Platform to build, ship, and run apps in containers from images. | | 47 | Dockerfile | Recipe describing how to build a container image. | | 48 | DRY | Don't Repeat Yourself β€” centralize shared logic instead of copying. | | 49 | E2E test | End-to-end test β€” full user flow through real UI and often backends. | | 50 | Encryption | Scrambling data so only key holders can read it. | | 51 | Environment variable | Named config injected at runtime (secrets, URLs, flags). | | 52 | Event loop | JS runtime scheduling callbacks, microtasks, and rendering. | | 53 | Event-driven architecture | Services react to messages/events instead of sync calls. | | 54 | EXPLAIN | SQL command showing how the database plans to execute a query. | | 55 | Fixture (testing) | Reusable setup/teardown object or data for tests. | | 56 | Flexbox | CSS one-dimensional layout along main/cross axis. | | 57 | Foreign key | Column referencing a primary key in another table. | | 58 | Functional programming | Style emphasizing pure functions, immutability, composition. | | 59 | Garbage collection | Automatic reclaim of memory no longer reachable. | | 60 | GraphQL | API style where clients request exact fields from one endpoint. | | 61 | gRPC | High-performance RPC using HTTP/2 and often Protocol Buffers. | | 62 | Hash / Hashing | One-way function mapping input to fixed-size digest. | | 63 | Hook (React) | Function like useState/useEffect using React features in function components. | | 64 | Horizontal scaling | Add more machines to handle load (scale out). | | 65 | HTML | HyperText Markup Language β€” semantic structure of web documents. | | 66 | HTTP | Hypertext Transfer Protocol β€” request/response protocol for the web. | | 67 | HTTPS | HTTP over TLS β€” encrypted and authenticated web traffic. | | 68 | Hydration | Attaching client JS handlers and state to server-rendered HTML. | | 69 | Idempotent | Repeating an operation yields the same result (safe retries). | | 70 | Image (Docker) | Immutable template for containers; layered and cached. | | 71 | Immutable | Value that cannot change after creation β€” copy instead of mutate. | | 72 | Index (DB) | Structure speeding lookups on columns at write/storage cost. | | 73 | Infrastructure as Code (IaC) | Define servers/networks in versioned files. | | 74 | Integration test | Tests several modules or services together. | | 75 | ISR | Incremental Static Regeneration β€” rebuild static pages on schedule/demand. | | 76 | JSON | JavaScript Object Notation β€” text format for structured API data. | | 77 | JSON Web Token (JWT) | Compact signed token encoding claims for stateless auth. | | 78 | Kubernetes (K8s) | Orchestrator scheduling, scaling, and healing containers. | | 79 | Latency | Time delay between request and response. | | 80 | Load balancer | Distributes traffic across servers for capacity and fault tolerance. | | 81 | Middleware | Code between request and handler (logging, auth, parsing). | | 82 | Microservices | Small independently deployable services with bounded contexts. | | 83 | Migration (DB) | Versioned schema change applied in order across environments. | | 84 | Mock (testing) | Test double replacing a dependency with controlled behavior. | | 85 | Monolith | Single deployable application containing most business logic. | | 86 | MVC | Model–View–Controller β€” separates data, UI, and request handling. | | 87 | mTLS | Mutual TLS β€” both client and server present certificates. | | 88 | NoSQL | Non-relational DB families: document, key-value, column, graph. | | 89 | Normalization | Organizing relational tables to reduce redundancy. | | 90 | OAuth 2.0 | Authorization framework delegating access via tokens without sharing passwords. | | 91 | OIDC | OpenID Connect β€” identity layer on OAuth issuing ID tokens. | | 92 | ORM | Object-Relational Mapper β€” maps tables/rows to application objects. | | 93 | Pagination | Splitting large results into pages (offset/limit or cursor). | | 94 | Primary key | Column(s) uniquely identifying each table row. | | 95 | Promise | JS object representing eventual completion/failure of async work. | | 96 | Prop (React) | Read-only input passed from parent to child component. | | 97 | Protocol Buffer | Binary serialization format often used with gRPC. | | 98 | Pub/Sub | Publish–subscribe messaging by topic. | | 99 | Pull request (PR) | Proposal to merge a branch; triggers review and CI. | | 100 | Query string | URL parameters after ? (e.g. ?q=python\&page=2). | | 101 | Queue | FIFO structure or broker decoupling producers and consumers. | | 102 | Race condition | Outcome depends on unpredictable timing of concurrent ops. | | 103 | Rate limiting | Cap requests per client/time window to protect availability. | | 104 | React | Library for UIs from components and declarative state. | | 105 | Redis | In-memory store for cache, sessions, pub/sub, and structures. | | 106 | Regression test | Ensures previously fixed features still work after changes. | | 107 | REST | HTTP APIs using resources, verbs, and status codes. | | 108 | Reverse proxy | Server in front of apps terminating TLS and routing. | | 109 | Rollback | Revert deployment to a known-good previous version. | | 110 | Server-side rendering (SSR) | HTML generated on the server per request. | | 111 | Serverless | Run functions on demand without managing servers yourself. | | 112 | Session | State tracking a user across requests (server or signed client). | | 113 | Sharding | Splitting data across DB instances by key range or hash. | | 114 | Smoke test | Quick sanity check that critical paths work after deploy. | | 115 | Snapshot test | Compare rendered output to a saved baseline file. | | 116 | SOLID | OOP design principles: SRP, OCP, LSP, ISP, DIP. | | 117 | SPA | Single Page App β€” client router swaps views without full reloads. | | 118 | SQL | Structured Query Language for relational data. | | 119 | SQL injection | Embedding SQL in user input; blocked by parameterized queries. | | 120 | SSG | Static Site Generation β€” HTML built at build time. | | 121 | SSL/TLS | Transport Layer Security β€” encrypts traffic and verifies identity. | | 122 | State (React) | Component-owned data that triggers re-render when updated. | | 123 | Stateless (HTTP) | Each request carries all context; no server session between calls. | | 124 | Stub (testing) | Fake implementation returning canned responses. | | 125 | TDD | Test-Driven Development β€” failing test first, then minimal code. | | 126 | Technical debt | Shortcuts that speed now but cost maintenance later. | | 127 | Throughput | Work completed per unit time (req/s, rows/s). | | 128 | TLS | Transport Layer Security β€” modern encrypted transport (successor to SSL). | | 129 | Transaction | DB operations that commit together or roll back on failure. | | 130 | Tree-shaking | Bundler removing unused exports from the final JS bundle. | | 131 | TypeScript | Typed superset of JavaScript compiling to plain JS. | | 132 | Unit test | Tests one function/module in isolation with mocks. | | 133 | Vertical scaling | Add CPU/RAM to one machine (scale up). | | 134 | Virtual DOM | In-memory tree diffed to update the real DOM efficiently. | | 135 | Webhook | HTTP callback when an external event happens. | | 136 | WebSocket | Full-duplex persistent connection for real-time messaging. | | 137 | White-box testing | Testing with knowledge of internal code paths. | | 138 | XSS | Cross-Site Scripting β€” injecting scripts viewed by other users. | | 139 | YAML | Human-readable data format common in CI and config. | | 140 | Zero-downtime deploy | Ship without users seeing outage (rolling, blue-green). | | 141 | ABI | Application Binary Interface β€” how compiled code calls libraries at machine level. | | 142 | Abstract class | Class that cannot be instantiated; may define partial behavior for subclasses. | | 143 | Acceptance test | Validates the system meets business/user requirements end-to-end. | | 144 | ACK | TCP acknowledgment packet confirming receipt of data. | | 145 | Active Record | ORM pattern where model objects wrap DB rows and know how to persist themselves. | | 146 | Affinity (K8s) | Schedule pods onto specific nodes (node affinity / anti-affinity). | | 147 | Aggregate (DDD) | Cluster of domain objects treated as one consistency boundary. | | 148 | Agile | Iterative delivery with short cycles, feedback, and adaptive planning. | | 149 | AJAX | Asynchronous JS + XML/JSON to update pages without full reloads. | | 150 | Alerting | Notify humans/systems when metrics cross thresholds (PagerDuty, etc.). | | 151 | Algorithm | Step-by-step procedure to solve a class of problems. | | 152 | Alias (Git) | Friendly name pointing to a commit (often a branch or tag). | | 153 | Amazon S3 | Object storage service β€” buckets of files with HTTP API. | | 154 | AMD (modules) | Asynchronous Module Definition β€” legacy JS module format. | | 155 | Amortized complexity | Average cost per operation over a sequence (e.g. dynamic array append). | | 156 | Annotation (Java/TS) | Metadata attached to code read by frameworks or compilers. | | 157 | Anonymous function | Function without a name β€” often inline or assigned to a variable. | | 158 | Ansible | Agentless configuration management using SSH and YAML playbooks. | | 159 | Anti-pattern | Common but counterproductive solution to a recurring problem. | | 160 | API key | Static secret identifying a client to an API (rotate and scope carefully). | | 161 | API versioning | Strategy to evolve APIs without breaking clients (/v1, headers, etc.). | | 162 | APM | Application Performance Monitoring β€” traces, metrics, errors in production. | | 163 | App Router (Next.js) | Next.js routing with layouts, RSC, and file-system routes under app/. | | 164 | Application layer (OSI) | Layer 7 β€” HTTP, DNS, SMTP; what most devs interact with. | | 165 | Argument (CLI) | Value passed to a command or flag on the shell. | | 166 | Array | Ordered collection addressable by index. | | 167 | Arrow function | JS concise function syntax with lexical this binding. | | 168 | ASCII | 7-bit character encoding for English letters and symbols. | | 169 | Aspect-oriented programming | Cross-cutting concerns (logging, auth) woven via aspects. | | 170 | Assertion | Check that expected condition holds in a test. | | 171 | Async I/O | Perform I/O without blocking the calling thread. | | 172 | Atomic operation | Operation that completes entirely or not at all from other threads' view. | | 173 | Attribute (HTML) | Name=value on an element modifying behavior or metadata. | | 174 | Authentication header | HTTP header carrying credentials (Authorization, Cookie, etc.). | | 175 | Auto-scaling | Automatically add/remove instances based on load metrics. | | 176 | Availability zone | Isolated datacenter area within a cloud region for redundancy. | | 177 | AVL tree | Self-balancing binary search tree maintaining height balance. | | 178 | B-tree | Balanced tree structure common in database indexes. | | 179 | Backpressure | Slowing producers when consumers cannot keep up. | | 180 | Backward compatibility | New versions still work with old clients/data formats. | | 181 | Bandwidth | Maximum data transfer rate of a link or service. | | 182 | Base64 | Encoding binary data as ASCII text for transport in JSON/email. | | 183 | Baseline (browser) | Reference browser list you support and test against. | | 184 | Batch processing | Process large datasets in grouped jobs rather than per-request. | | 185 | Benchmark | Timed measurement comparing performance of code or systems. | | 186 | Big O notation | Upper bound on growth rate of time/space vs input size. | | 187 | Binary search | Search sorted array by halving the range β€” O(log n). | | 188 | Binary tree | Tree where each node has at most two children. | | 189 | Binding (DNS) | Map hostname to IP or other records. | | 190 | Bit | Smallest unit of data β€” 0 or 1. | | 191 | Bitmask | Integer used as flags via bitwise AND/OR operations. | | 192 | Blob storage | Store unstructured binary objects (images, backups) by key. | | 193 | Block cipher | Encrypts fixed-size blocks (AES) vs stream ciphers. | | 194 | Blocking call | Call that waits until operation completes before returning. | | 195 | Bloom filter | Probabilistic set membership β€” may false-positive, never false-negative. | | 196 | Blueprint (software) | Detailed design describing components before implementation. | | 197 | Boolean | Logical true/false value type. | | 198 | Bootstrapping | Starting a process from minimal initial resources (compiler, cluster). | | 199 | Border-box (CSS) | width/height include padding and border, not just content. | | 200 | Bounded context (DDD) | Explicit boundary where a domain model and language apply. | | 201 | Box model (CSS) | Content, padding, border, margin layers of an element. | | 202 | Breakpoint (CSS) | Media query width where layout rules change. | | 203 | Breakpoint (debug) | Pause execution at a line to inspect state. | | 204 | Broadcast (network) | Send packet to all hosts on a subnet. | | 205 | Browser cache | Store assets locally to speed repeat visits. | | 206 | Buffer | Temporary memory holding data during transfer or processing. | | 207 | Buffer overflow | Writing past allocated memory β€” classic security bug. | | 208 | Build cache | Reuse prior build outputs to speed CI (Docker layers, npm cache). | | 209 | Bulkhead pattern | Isolate resources so failure in one pool cannot drain all. | | 210 | Bundle (JS) | Packaged output combining modules for the browser. | | 211 | Bytecode | Intermediate instructions VMs execute (JVM, CPython, WASM). | | 212 | Cache invalidation | Remove or refresh stale cached entries when source changes. | | 213 | Cache stampede | Many requests miss cache simultaneously and hammer origin. | | 214 | Caching header | HTTP headers (Cache-Control, ETag) controlling CDN/browser cache. | | 215 | Call stack | LIFO record of active function calls during execution. | | 216 | CamelCase | Naming style joining words with capital letters (myVariable). | | 217 | Canary analysis | Compare metrics between canary and baseline during rollout. | | 218 | Cardinality | Number of distinct values in a set or metric label set. | | 219 | Cascading (CSS) | How styles from multiple sources combine and inherit. | | 220 | CDN cache hit | Response served from edge without reaching origin. | | 221 | Cell (spreadsheet/table) | Single intersection of row and column. | | 222 | Certificate pinning | App trusts only specific cert/public key, not whole CA chain. | | 223 | Character encoding | Mapping bytes to characters (UTF-8, Latin-1). | | 224 | Checksum | Hash-like value detecting accidental data corruption. | | 225 | Cherry-pick (Git) | Apply a specific commit onto another branch. | | 226 | Chunk (webpack) | Split bundle piece loaded on demand (code splitting). | | 227 | Circuit breaker | Stop calling failing dependency until it recovers. | | 228 | Class (OOP) | Blueprint for objects with fields and methods. | | 229 | CLI | Command-Line Interface β€” text commands in a terminal. | | 230 | Client certificate | TLS cert presented by client for mutual authentication. | | 231 | Cloud region | Geographic area hosting cloud resources (us-east-1). | | 232 | Cluster (K8s) | Group of nodes running container workloads. | | 233 | CMS | Content Management System β€” edit site content without code deploys. | | 234 | Code coverage | Percentage of source lines/branches executed by tests. | | 235 | Code review | Peer inspection of changes before merge. | | 236 | Code splitting | Load only JS needed for current route/feature. | | 237 | Cohesion | How closely related responsibilities within a module are. | | 238 | Cold start | Latency when spinning up new serverless/container instance from idle. | | 239 | Column store | DB storing columns together β€” good for analytics scans. | | 240 | Command pattern | Encapsulate request as object with execute/undo. | | 241 | Commit (Git) | Snapshot of repository state with message and parent pointer. | | 242 | Compile time | When source is translated to bytecode/binary before running. | | 243 | Compiler | Translates entire program ahead of time (C, Rust, TSβ†’JS). | | 244 | Composite index | DB index on multiple columns together. | | 245 | Composition (React) | Build UI by nesting components instead of inheritance. | | 246 | Compression | Reduce bytes (gzip, brotli) for faster transfer. | | 247 | Concurrency | Multiple tasks making progress (not necessarily parallel). | | 248 | Conditional rendering | Show UI based on boolean state or props. | | 249 | Config map (K8s) | Key-value config injected into pods as env or files. | | 250 | Constructor | Function initializing a new object instance. | | 251 | Container image registry | Store for images (Docker Hub, ECR, GHCR). | | 252 | Content Security Policy (CSP) | HTTP header restricting script/style sources to reduce XSS. | | 253 | Continuous profiling | Sample production CPU/memory to find hot paths. | | 254 | Control flow | Order in which statements and branches execute. | | 255 | Controlled component | Form input whose value is driven by React state. | | 256 | Cookie attributes | HttpOnly, Secure, SameSite β€” control cookie behavior. | | 257 | Copy-on-write | Share memory until a write forces a duplicate (fork, persistent DS). | | 258 | Coroutine | Function that can suspend/resume cooperatively (async def, Go). | | 259 | Coupling | Degree of dependency between modules β€” lower is often better. | | 260 | CPU-bound | Work limited by processor speed, not I/O wait. | | 261 | Crawler | Automated bot fetching pages (search engines, scrapers). | | 262 | Credential stuffing | Attack reusing leaked passwords on many sites. | | 263 | Cron | Time-based job scheduler syntax (minute hour day month weekday). | | 264 | Cross-site cookie | Cookie sent on cross-origin requests β€” restricted by SameSite. | | 265 | CRDT | Conflict-free Replicated Data Type β€” merge without coordination. | | 266 | Cryptographic salt | Random data mixed into password hashing to defeat rainbow tables. | | 267 | CSRF token | Unpredictable value proving form POST came from your site. | | 268 | Cursor (DB) | Database iterator over query results row-by-row. | | 269 | Cursor pagination | Page using opaque cursor token instead of OFFSET. | | 270 | Daemon process | Background service not tied to an interactive terminal. | | 271 | Dark launch | Ship code to prod disabled or internal-only before user exposure. | | 272 | Data class | Class mainly holding data with generated boilerplate (Python @dataclass). | | 273 | Data lake | Large store of raw structured/unstructured data for analytics. | | 274 | Data warehouse | Optimized analytical DB for reporting (Snowflake, BigQuery). | | 275 | Database replica | Read-only copy of primary for scaling reads. | | 276 | Database view | Saved query acting like a virtual table. | | 277 | Debounce | Wait until events stop firing before acting (search input). | | 278 | Decoupling | Reduce direct dependencies between components. | | 279 | Default export | Module's primary export (one per ES module file). | | 280 | Defensive programming | Validate inputs and fail safely anticipating misuse. | | 281 | Delegation | Forward work to another object instead of doing it yourself. | | 282 | Denormalization | Duplicate data in DB to speed reads at cost of write complexity. | | 283 | Dependency | External library or service your code relies on. | | 284 | Dependency graph | Directed graph of package/module dependencies. | | 285 | Deployment pipeline | Automated stages from commit to production. | | 286 | Deprecation | Mark API/feature as scheduled for removal; warn callers. | | 287 | Descriptor (Python) | Object defining **get**/**set** controlling attribute access. | | 288 | Design pattern | Reusable solution to a recurring design problem. | | 289 | Destructuring | Unpack object/array fields into variables in one statement. | | 290 | Dev container | Development environment defined as a container spec. | | 291 | DevSecOps | Integrate security checks into dev and CI workflows. | | 292 | DHCP | Protocol assigning IP addresses automatically on a network. | | 293 | Diff (Git) | Line-by-line comparison between commits or files. | | 294 | Digest (HTTP) | Hash of body used for integrity (Content-Digest). | | 295 | Digital signature | Cryptographic proof that data came from holder of private key. | | 296 | Dijkstra algorithm | Shortest path in weighted graph with non-negative edges. | | 297 | Directory traversal | Attack accessing files outside intended path via ../ sequences. | | 298 | Dirty read | Reading uncommitted data from another transaction. | | 299 | Distributed lock | Coordinate exclusive access across multiple nodes (Redis, etcd). | | 300 | Distributed tracing | Follow one request across services with trace/span IDs. | | 301 | DNS propagation | Time for DNS record changes to spread globally. | | 302 | Docker Compose | YAML defining multi-container apps for local/dev. | | 303 | Docker layer | Immutable filesystem diff stacked into an image. | | 304 | Document store | NoSQL DB storing JSON-like documents (MongoDB). | | 305 | Domain name | Human-readable hostname (example.com). | | 306 | Double dispatch | Method chosen based on runtime types of two objects. | | 307 | Downtime | Period when service is unavailable to users. | | 308 | Dynamo-style DB | Highly available key-value store with eventual consistency (DynamoDB). | | 309 | Edge computing | Run logic near users/devices instead of central datacenter. | | 310 | Edge function | Serverless function at CDN edge for low latency. | | 311 | ElasticSearch | Search/analytics engine built on inverted indexes. | | 312 | Element (DOM) | Node representing an HTML tag in the document tree. | | 313 | Encapsulation | Hide internal state; expose behavior via public interface. | | 314 | Entity (DDD) | Object with identity persisting over time (User, Order). | | 315 | Enum | Type or construct for fixed set of named constants. | | 316 | Ephemeral container | Temporary debug container attached to a pod. | | 317 | Ephemeral storage | Non-persistent disk in containers/pods β€” lost on restart. | | 318 | Error boundary (React) | Component catching render errors in child tree. | | 319 | ES modules | Standard JS import/export module system (import/export). | | 320 | Escape hatch | API to break abstraction when special case requires it. | | 321 | ETag | HTTP validator token for conditional GET and cache revalidation. | | 322 | Event bubbling | DOM events propagate from target up to ancestors. | | 323 | Event capturing | DOM events propagate from root down to target. | | 324 | Event sourcing | Store state changes as append-only event log. | | 325 | Eventually consistent | Replicas converge over time; reads may be stale briefly. | | 326 | Exception | Object thrown to signal error and unwind stack. | | 327 | Exponential backoff | Retry delays grow exponentially to reduce load on failures. | | 328 | Export (module) | Expose bindings from a module to importers. | | 329 | Express.js | Minimal Node.js web framework for HTTP APIs. | | 330 | Extension method | Add methods to existing types without modifying source (Kotlin, C#). | | 331 | Failover | Automatically switch to backup when primary fails. | | 332 | Fallback | Alternative path when primary option fails (fonts, CDN). | | 333 | Fan-out | One producer sends to many consumers. | | 334 | Fan-in | Many producers send to one consumer/aggregator. | | 335 | Fastify | Fast Node.js web framework with schema-based validation. | | 336 | Feature flag | Toggle behavior at runtime without redeploying code. | | 337 | Feature branch | Short-lived branch for one feature or fix. | | 338 | Federal Identity | Government/regulated identity standards (less common in web dev). | | 339 | Fiber (React) | Reconciliation engine enabling incremental rendering and priorities. | | 340 | FIFO | First In, First Out β€” queue discipline. | | 341 | File descriptor | OS handle representing open file, socket, or pipe. | | 342 | Filter (CSS) | Visual effects like blur/brightness on elements. | | 343 | Finalizer | Cleanup hook when object is garbage-collected (avoid for resources). | | 344 | Firewall | Network rules allowing/denying traffic by port/IP. | | 345 | First-class function | Functions treated as values β€” passed and returned freely. | | 346 | Fixed-point arithmetic | Decimal math without floating rounding errors. | | 347 | Flaky test | Test that intermittently fails without code changes. | | 348 | Flash storage | SSD/NVMe β€” fast non-volatile storage. | | 349 | Floating point | IEEE format approximating real numbers β€” beware rounding. | | 350 | Fluent interface | Method chaining returning this for readable APIs. | | 351 | Fuzz testing | Random/mutated inputs to find crashes and edge cases. | | 352 | Garbage collection pause | Stop-the-world interval while GC runs. | | 353 | Gateway (API) | See API Gateway β€” entry point for microservices. | | 354 | Generics | Type parameters letting code work across types safely. | | 355 | Git fetch | Download remote commits without merging into local branch. | | 356 | Git merge | Combine branch histories creating merge commit if needed. | | 357 | Git rebase | Replay commits onto new base for linear history. | | 358 | Git stash | Temporarily shelve uncommitted changes. | | 359 | Git tag | Immutable pointer to a release commit. | | 360 | GitHub Actions | CI/CD workflows triggered by GitHub events. | | 361 | GitOps | Git as source of truth; automation syncs cluster to repo state. | | 362 | Global scope | Variables visible everywhere in a script (avoid polluting). | | 363 | Global variable | Variable accessible across entire program β€” tight coupling risk. | | 364 | Graceful shutdown | Finish in-flight work and close connections before exit. | | 365 | Graph (data structure) | Nodes and edges modeling relationships. | | 366 | Graph database | Store optimized for traversing relationships (Neo4j). | | 367 | Greedy algorithm | Pick locally best choice hoping for global optimum. | | 368 | Grid (CSS) | See CSS Grid β€” 2D layout system. | | 369 | Guard clause | Early return on invalid conditions to reduce nesting. | | 370 | GUI | Graphical User Interface β€” windows, buttons, mouse-driven. | | 371 | Gzip | Compression algorithm common for HTTP responses. | | 372 | Handshake (TLS) | Negotiate cipher suite and keys before encrypted data. | | 373 | Hard link | Directory entry pointing to same inode as another name. | | 374 | Hash collision | Two inputs producing same hash β€” rare but possible. | | 375 | Hash map | Key-value structure with O(1) average lookup via hashing. | | 376 | Hash table | See hash map β€” array of buckets with collision handling. | | 377 | Headless CMS | Content API without bundled frontend (Contentful, Sanity). | | 378 | Headless component | UI logic without styles β€” bring your own CSS. | | 379 | Health check | Endpoint or probe reporting if service is alive/ready. | | 380 | Heap (memory) | Region for dynamic allocation (malloc/new). | | 381 | Heap (data structure) | Priority queue β€” min/max element at root. | | 382 | Helm chart | Packaged K8s manifests with templated values. | | 383 | Hexadecimal | Base-16 numbering (0-9, A-F) common for colors and bytes. | | 384 | Hidden class (JS engine) | V8 internal shape optimization for object layouts. | | 385 | HMAC | Hash-based Message Authentication Code β€” integrity + secret. | | 386 | Hoisting (JS) | Declarations moved to top of scope during compilation. | | 387 | Hot reload | Apply code changes without full app restart (dev UX). | | 388 | Hot path | Code executed most frequently β€” optimize here first. | | 389 | HTTP/2 | Multiplexed streams, header compression, binary framing. | | 390 | HTTP/3 | HTTP over QUIC (UDP) β€” faster connection setup. | | 391 | HTTP method | Verb: GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS. | | 392 | HTTP status code | 3-digit result: 2xx success, 4xx client error, 5xx server. | | 393 | Hub (React Native) | Central native module bridge for RN apps. | | 394 | Hypervisor | Software running VMs (KVM, Hyper-V) or managing containers. | | 395 | I/O bound | Work limited by disk/network latency, not CPU. | | 396 | IaaS | Infrastructure as a Service β€” VMs, networks, raw compute (EC2). | | 397 | Idempotency key | Client token ensuring retried POST does not duplicate side effects. | | 398 | Idempotent consumer | Message handler safe if same message delivered twice. | | 399 | IDE | Integrated Development Environment β€” editor + debugger + tools. | | 400 | Immutable infrastructure | Replace servers instead of patching in place. | | 401 | Import (module) | Load bindings exported from another module. | | 402 | In-memory database | Data lives in RAM β€” fast, often non-durable (Redis). | | 403 | Inbound rule | Firewall/security group allowing incoming traffic. | | 404 | Incident response | Process to detect, mitigate, and learn from outages. | | 405 | IndexedDB | Browser key-value store for large structured client data. | | 406 | Inference | Run trained ML model to produce predictions. | | 407 | Inheritance (OOP) | Subclass acquires fields/methods from parent class. | | 408 | Ingress (K8s) | Routes external HTTP/S traffic into cluster services. | | 409 | Injection attack | Insert malicious input interpreted as code (SQL, XSS, command). | | 410 | Inline style | CSS declared on element style attribute β€” high specificity. | | 411 | Inner join | SQL join returning rows with matching keys in both tables. | | 412 | Input validation | Reject malformed data at boundary before processing. | | 413 | Instance (cloud) | Virtual machine or container running your workload. | | 414 | Integer overflow | Result exceeds representable range wrapping or erroring. | | 415 | Interface (OOP/TS) | Contract listing methods a type must implement. | | 416 | Interface segregation | SOLID: many specific interfaces beat one fat interface. | | 417 | Interpreter | Executes source line-by-line (Python, Ruby shell). | | 418 | Inversion of control | Framework calls your code (callbacks, DI containers). | | 419 | Inverted index | Map from term to documents containing it β€” core of search engines. | | 420 | IP address | Numeric host identifier (IPv4 32-bit, IPv6 128-bit). | | 421 | IPv6 | 128-bit addresses solving IPv4 exhaustion. | | 422 | ISO 8601 | Standard date/time string format (2026-07-11T13:00:00Z). | | 423 | Isolation level | SQL transaction visibility rules (READ COMMITTED, SERIALIZABLE). | | 424 | Issue tracker | System for bugs/tasks (Jira, GitHub Issues). | | 425 | Iterable | Object producing sequence via **iter** or Symbol.iterator. | | 426 | Iterator | Object with next() yielding items until done. | | 427 | Jenkins | Self-hosted CI server with plugins and pipelines. | | 428 | Jitter | Randomness added to retry/backoff to prevent thundering herd. | | 429 | Job queue | Workers pull tasks from queue (Sidekiq, Celery, Bull). | | 430 | Join (SQL) | Combine rows from tables on related keys. | | 431 | JPEG | Lossy image compression common for photos. | | 432 | JSON Schema | Vocabulary validating JSON document structure. | | 433 | JSONB | Postgres binary JSON with indexing and efficient storage. | | 434 | JVM | Java Virtual Machine β€” runs bytecode with GC and JIT. | | 435 | JWT refresh token | Long-lived token used only to obtain new access tokens. | | 436 | K-nearest neighbors | ML classification by majority vote of closest training points. | | 437 | Kafka | Distributed log/stream platform for high-throughput events. | | 438 | Key-value store | DB indexed by single key (Redis, DynamoDB). | | 439 | Kubernetes Deployment | Declarative desired state for ReplicaSets and rolling updates. | | 440 | Kubernetes Namespace | Virtual cluster partition for resources and quotas. | | 441 | Kubernetes Pod | Smallest deployable unit β€” one or more containers sharing network. | | 442 | Kubernetes Service | Stable virtual IP/DNS load-balancing to pods. | | 443 | Lambda (AWS) | Serverless function service triggered by events. | | 444 | Lambda (functional) | Anonymous inline function (Python lambda, JS arrow). | | 445 | Latency p99 | 99th percentile response time β€” tail latency metric. | | 446 | Layer (network) | OSI/TCP-IP abstraction level (link, network, transport, app). | | 447 | Lazy evaluation | Compute value only when first needed (generators, Suspense). | | 448 | Lazy loading | Load resource (image, route) when it enters viewport or route. | | 449 | Leader election | Pick one coordinator node in distributed system. | | 450 | Leaf node | Tree node with no children. | | 451 | Legacy code | Existing system hard to change but still in production. | | 452 | Lighthouse | Chrome tool auditing performance, a11y, SEO, PWA. | | 453 | LIFO | Last In, First Out β€” stack discipline. | | 454 | Lift (SQL) | Apply function to every row/column without explicit loop. | | 455 | Lighthouse score | 0–100 ratings from automated web audits. | | 456 | Linter | Static analyzer flagging style and likely bugs (ESLint, Ruff). | | 457 | Linked list | Nodes pointing to next β€” O(1) insert, O(n) index access. | | 458 | Linkerd | Service mesh providing mTLS, metrics, retries for microservices. | | 459 | Lint-staged | Run linters only on staged git files in pre-commit. | | 460 | Linux namespace | Kernel isolation for PID, network, mount (container basis). | | 461 | Load shedding | Drop/defer requests when overloaded to protect core service. | | 462 | LocalStorage | Browser persistent key-value storage per origin. | | 463 | Lock (mutex) | Ensure only one thread enters critical section. | | 464 | Log aggregation | Centralize logs from many hosts (ELK, Loki). | | 465 | Log level | Severity filter: debug, info, warn, error. | | 466 | Log rotation | Archive and truncate logs so disks do not fill. | | 467 | Logging | Record events with context for debugging and audit. | | 468 | Long polling | HTTP request held open until server has data to push. | | 469 | Loose coupling | Components interact via stable interfaces, not internals. | | 470 | LSP (Liskov) | Subtypes must be substitutable for base types without surprises. | | 471 | LTS | Long-Term Support release with extended security fixes. | | 472 | Machine learning | Models learned from data rather than explicit rules. | | 473 | Macro (Rust/C) | Compile-time code generation or text substitution. | | 474 | Manifest (PWA) | JSON describing app name, icons, start URL for install. | | 475 | Map (data structure) | Associative array β€” keys to values (dict, Map, object). | | 476 | Markdown | Lightweight plain-text formatting (headings, lists, code fences). | | 477 | Marshalling | Convert in-memory data to wire format (JSON, protobuf). | | 478 | Memory leak | Memory never freed β€” usage grows until crash. | | 479 | Memoization | Cache function results keyed by arguments. | | 480 | Merge conflict | Git cannot auto-merge overlapping edits β€” manual resolution. | | 481 | Message broker | Middleware routing messages between producers/consumers. | | 482 | Message queue | Async buffer decoupling senders and receivers. | | 483 | Metadata | Data about data β€” tags, headers, schema info. | | 484 | Method overloading | Same method name, different parameter lists (Java, C#). | | 485 | Method overriding | Subclass replaces parent method implementation. | | 486 | Metric | Numeric measurement over time (CPU, RPS, error rate). | | 487 | Microtask | High-priority JS task after current stack (Promise callbacks). | | 488 | Middleware (Express) | Function (req,res,next) in request pipeline. | | 489 | MIME type | Media type label (text/html, image/png). | | 490 | Minification | Remove whitespace and shorten names in JS/CSS for size. | | 491 | Mirror (Git) | Copy of remote repo hosted elsewhere (GitHub mirror). | | 492 | MitM attack | Man-in-the-Middle β€” intercept traffic between parties. | | 493 | Mixin | Class/module providing reusable methods to multiple classes. | | 494 | Module bundler | Tool packing modules for browser (webpack, Vite, esbuild). | | 495 | Module federation | Share JS modules across independently deployed apps. | | 496 | Monorepo | Single repository containing multiple packages/services. | | 497 | Monte Carlo | Random sampling method for estimation/simulation. | | 498 | Mount (React) | Attach component to DOM and run effects first time. | | 499 | Multi-factor auth (MFA) | Require two+ proof factors (password + TOTP). | | 500 | Multi-tenancy | One app instance serves isolated customers (tenants). | ## πŸ’‘ Examples [#-examples] **Quick recall drill β€” define in one sentence:** 1. **JWT** β€” Signed token carrying claims so APIs can authenticate without server session storage. 2. **ORM** β€” Maps DB tables to objects so you query with code instead of raw SQL everywhere. 3. **Black-box testing** β€” Verify outputs for inputs without inspecting source implementation. 4. **CI/CD** β€” Automate build/test on every change and promote passing artifacts to environments. 5. **Circuit breaker** β€” Stop calling a failing dependency until it recovers, preventing cascade failures. **Interview follow-ups:** * TLS vs HTTPS vs mTLS * Unit vs integration vs E2E vs smoke * REST vs GraphQL trade-offs * SSR vs SSG vs CSR vs ISR * OAuth vs session cookie vs JWT * CAP vs PACELC for distributed databases ## ⚠️ Pitfalls [#️-pitfalls] * Confusing **authentication** (who) with **authorization** (what they may do). * Saying JWT is β€œmore secure” than sessions β€” depends on storage, expiry, and rotation. * Treating **CI** and **CD** as the same β€” integration vs delivery vs deployment differ. * **Black-box** does not mean β€œno tests of internals ever” β€” choose level by risk. * Memorizing **500 terms** without examples β€” pair each with one real project use case. ## πŸ”— Related [#-related] * Per-topic glossaries under each stack (Python, Docker, React, etc.) * [Comparisons](/docs/global-glossary/../comparisons) β€” A vs B trade-off notes * [Coverage](/docs/coverage) β€” which topics have glossary pages