Daily micro-tips for C#, SQL, performance, and scalable backend engineering.
Array.forEach() does not await async functions.This silently causes race conditions and partial execution. // ❌ This does NOT wait items.forEach(async item => { await process(item); }); // ✅ Correct for (const item of items) { await process(item); } Why this mattersforEach ignores promises. Errors get swallowed, execution order breaks.
Network OK, UI frozen. Why it happensState updated outside render cycle. Why it mattersUsers see stale data. Vital fix Centralize state updates.
No leaks visible. Why it happensDetached DOM references. Why it mattersLong sessions slow down. Vital fix Null references explicitly.
Intervals lose accuracy. Why it happenssetInterval stacks delays. Why it mattersAnimations and polling drift. Smart fixUse recursive setTimeout.
No crash, slow death. Why it happensDetached DOM references. Why it mattersLong-running apps degrade silently. Smart fixClear references on element removal. element = null;
Users click once. WhyButton not disabled during request. TipDisable button until response. button.disabled = true;
Small loops, big impact. WhyDOM updates inside loops. TipBatch DOM changes. const fragment = document.createDocumentFragment();
Correct response, old UI. WhyClient-side caching assumptions. TipExplicitly control cache headers.
SPA feels heavier over time. WhyEvent listeners not removed. TipAlways clean up listeners on teardown.
Data arrives, UI lags. WhyDOM updates are too frequent. TipBatch DOM updates after Ajax responses.
Same logic, rising memory. WhyInline object creation inside loops. TipMove static objects outside loops. const config = {}; for (…) { use(config); }
Same code, different behavior. WhyImplicit type coercion. TipUse strict comparisons everywhere. if (value === 0) { }
Data loads fine, battery suffers. WhyPolling instead of event-driven updates. Tip Use push or conditional polling.
Page feels heavier over time. WhyListeners accumulate without cleanup. Tip Remove listeners when components unmount.
UI freezes briefly. WhyHeavy JSON parsing on main thread. Tip Offload parsing to Web Workers.
No obvious leaks. WhyLong-lived references in closures. Tip Explicitly null references after use.
Desktop fine. Mobile broken. WhyMobile networks aggressively drop idle connections. Fix Set shorter request timeouts.
No leak detected. WhyReferences are retained by closures. Fix Explicitly clear arrays when lifecycle ends.
Server updated, client not. WhyAggressive caching on GET requests. Fix Add cache-busting headers or query tokens.
Intervals slowly become inaccurate. WhysetInterval depends on event loop timing. Fix Recalculate timing based on actual timestamps.
Direct calls succeed. WhyMissing forwarded headers. FixForward X-Forwarded-Proto.
No visible leaks. WhyDetached DOM nodes remain referenced. FixExplicitly null unused references.
No errors, no data. WhyServer closes connection before body flush. FixExplicitly flush response on server side.
Intervals lose accuracy. WhysetInterval accumulates delay. Fix Use recursive setTimeout with timestamps.
Works when tab is active. WhyBrowser throttles background requests. FixUse Background Sync or retry logic.
UI renders stale data. WhyState mutations are asynchronous. Fix setState(prev => ({ …prev, value }));
Fast internet hides the bug. WhyRace conditions between requests. FixCancel in-flight requests before sending new ones.
One click triggers multiple handlers. WhyListeners added repeatedly without removal. Fix element.removeEventListener(‘click’, handler);
No errors, no data. WhyCORS preflight blocked. FixAllow OPTIONS requests on server.
Code runs, logic breaks. WhyforEach ignores await. Fix for (const item of items) { await process(item); }