Node.js Latency Measurement and Event Loop Delay
Measure Node.js latency without fooling yourself: monotonic clocks, percentiles over averages, coordinated omission, and event loop delay and ELU.
~7 min readread →
Developer interview notes & guides — Page 7
Focused explanations and longer guides, with worked scenarios, common mistakes and interview exercises across every chapter.
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Showing 145–168 of 200 articles
Node.js stream.pipeline() vs .pipe(): Handling Stream Errors
Why .pipe() leaks the source when a destination fails, what pipeline() destroys for you, and what a client sees when an export breaks halfway.
~6 min readread →
Node.js Streams and Backpressure
What write() returning false means, how ignoring it buffered 197 MB for one slow client, and why awaiting drain alone hangs on a disconnect.
~7 min readread →
Node.js Test Isolation and Async Completion
Why an unawaited assert.rejects passes, how one unclosed server hung a test file, and node:test patterns that keep each test's state its own.
~7 min readread →
Node.js Timers and Scheduling Guarantees
setTimeout promises a minimum delay, not a time. Measured drift, skipped interval ticks, and how to build a countdown that stays correct.
~7 min readread →
Node.js Worker Threads and CPU Parallelism
On Node 22 a worker cut main-thread lag from 455 ms to 1 ms, yet a new worker per tiny task was 550x slower. Build a bounded pool instead.
~8 min readread →
React Dialogs: Focus, Escape and Restoration
Build an accessible React modal: native dialog with showModal, focus on open, Escape to close, focus restoration and testing with keyboard only.
~7 min readread →
React Derived Values Without Extra State
Stop syncing state with useEffect: compute filtered lists, totals and validity during render in React, and use useMemo only for real cost.
~6 min readread →
React useEffect Cleanup: When It Runs and How to Avoid Leaks
When React runs useEffect cleanup, why Strict Mode mounts twice, and how to clean up listeners, timers, sockets and fetches without leaks.
~7 min readread →
React Error Boundaries and Recovery Scope
What React error boundaries catch and miss, where to place them so one failing widget does not blank the page, and how to reset after errors.
~7 min readread →
React External Stores and Consistent Snapshots
How useSyncExternalStore subscribes React to an external store without tearing, why getSnapshot must be cached, and how server snapshots work.
~6 min readread →
React Hydration and Matching Initial Content
What causes React hydration mismatch errors: dates, random ids, window checks and bad HTML nesting, plus fixes with useId, effects and Suspense.
~7 min readread →
React List Keys: Why Index Keys Break State
Why React list keys matter: how index keys attach state to the wrong row after deletes or reordering, and how to pick a stable, unique key.
~6 min readread →
React Reducers and Valid State Transitions
When to choose useReducer over useState: model status as one field, reject impossible transitions in the reducer, and test it in plain Node.
~6 min readread →
React Refs Versus State for Mutable Values
useRef vs useState in React: refs change without re-rendering, state drives the UI. Learn which values belong where, with timer and DOM examples.
~6 min readread →
React Resetting Forms With Component Keys
Reset a React form when the selected record changes by giving it a key: how keys control state identity and why useEffect resets go wrong.
~6 min readread →
Spring Actuator Exposure and Operational Access
Which Spring Boot Actuator endpoints to expose, how exposure differs from authorization, and how to lock down env, heapdump and health details.
~7 min readread →
Spring Boot Auto-Configuration and Explicit Overrides
How Spring Boot auto-configuration works: AutoConfiguration.imports, @ConditionalOnMissingBean, the conditions report, and safe overrides.
~7 min readread →
Spring CSRF Protection and Authentication Transport
When Spring Security CSRF protection is needed: cookie sessions vs bearer tokens, SameSite, CookieCsrfTokenRepository and SPA setups in Boot 3.
~6 min readread →
Spring Controller Advice and Error Responses
Map Spring Boot exceptions to stable HTTP errors with @RestControllerAdvice and ProblemDetail, without leaking stack traces or internals.
~6 min readread →
Spring Boot RestClient and WebClient Timeouts: How to Set Them
Set connect and read timeouts on Spring RestClient and WebClient, size them from a latency budget, and stop slow calls exhausting threads.
~7 min readread →
LazyInitializationException in Spring Boot JPA: Causes and Fixes
Why Hibernate throws LazyInitializationException in Spring Boot, how open-in-view hides it, and how fetch joins, entity graphs and DTOs fix it.
~6 min readread →
Spring JPA Optimistic Locking and Conflicts
How JPA @Version prevents lost updates in Spring Boot, what ObjectOptimisticLockingFailureException means, and when to retry or return 409.
~7 min readread →
@DataJpaTest vs Testcontainers: Testing Spring Data Repositories
What @DataJpaTest loads, why its rollback and embedded database can hide bugs, and how to test Spring Data repositories with Testcontainers.
~6 min readread →
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