Fix: Jest Fake Timers Not Working — setTimeout and setInterval Not Advancing
How to fix Jest fake timers not working — useFakeTimers setup, runAllTimers vs advanceTimersByTime, async timers, React testing with act(), and common timer test mistakes.
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Fix: Jest Module Mock Not Working — jest.mock() Has No Effect
How to fix Jest module mocks not working — hoisting behavior, ES module mocks, factory functions, mockReturnValue vs implementation, and clearing mocks between tests.
Fix: Kubernetes Secret Not Mounted — Pod Cannot Access Secret Values
How to fix Kubernetes Secrets not being mounted — namespace mismatches, RBAC permissions, volume mount configuration, environment variable injection, and secret decoding issues.
Fix: MySQL Index Not Being Used — Query Optimizer Skipping Indexes
How to fix MySQL indexes not being used by the query optimizer — EXPLAIN output, implicit conversions, function on columns, composite index order, cardinality issues, and forcing indexes.
Fix: NestJS Guard Not Working — canActivate Always Passes or Is Never Called
How to fix NestJS guards not working — applying guards globally vs controller vs method level, JWT AuthGuard, metadata with Reflector, public routes, and guard execution order.
Fix: NestJS Interceptor Not Triggered — Interceptors Not Running
How to fix NestJS interceptors not being called — global vs controller vs method binding, response transformation, async interceptors, execution context, and interceptor ordering.
Fix: Node.js UnhandledPromiseRejection and uncaughtException — Crashing Server
How to handle Node.js uncaughtException and unhandledRejection events — graceful shutdown, error logging, async error boundaries, and keeping servers alive safely.
Fix: Prisma N+1 Query Problem — include, select, and Relation Loading
How to fix the N+1 query problem in Prisma — using include and select for eager loading, fluent API pitfalls, DataLoader integration, and query logging to detect N+1 patterns.
Fix: Prisma Transaction Error — Transaction Already Closed or Rolled Back
How to fix Prisma transaction errors — interactive transactions vs $transaction array, error handling and rollback, nested transactions, timeout issues, and isolation levels.
Fix: Python asyncio Blocking the Event Loop — Mixing Sync and Async Code
How to fix Python asyncio event loop blocking — using run_in_executor for sync calls, asyncio.to_thread, avoiding blocking I/O in coroutines, and detecting event loop stalls.
Fix: Python Circular Import Error — ImportError and Cannot Import Name
How to fix Python circular import errors — restructuring modules, lazy imports, TYPE_CHECKING guard, dependency injection, and __init__.py import order issues.
Fix: React Hydration Error — Text Content Does Not Match
How to fix React hydration errors — server/client HTML mismatches, useEffect for client-only code, suppressHydrationWarning, dynamic content, and Next.js specific hydration issues.