Fix: AWS ECS Task Failed to Start
How to fix ECS tasks that fail to start — port binding errors, missing IAM permissions, Secrets Manager access, essential container exit codes, and health check failures.
Tag: backend
14 articles
Fix: Docker Multi-Stage Build COPY --from Failed
How to fix Docker multi-stage build errors — COPY --from stage not found, wrong stage name, artifacts not at expected path, and BuildKit caching issues.
Fix: Express req.body Is undefined
How to fix req.body being undefined in Express — missing body-parser middleware, wrong Content-Type header, middleware order issues, and multipart form data handling.
Fix: Flask Route Returns 404 Not Found
How to fix Flask routes returning 404 — trailing slash redirect, Blueprint prefix issues, route not registered, debug mode, and common URL rule mistakes.
Fix: Hibernate LazyInitializationException — Could Not Initialize Proxy
How to fix Hibernate LazyInitializationException — loading lazy associations outside an active session, fetch join, @Transactional scope, DTO projection, and Open Session in View.
Fix: Linux OOM Killer Killing Processes (Out of Memory)
How to fix Linux OOM killer terminating processes — reading oom_kill logs, adjusting oom_score_adj, adding swap, tuning vm.overcommit, and preventing memory leaks.
Fix: TypeScript Decorators Not Working (experimentalDecorators)
How to fix TypeScript decorators not applying — experimentalDecorators not enabled, emitDecoratorMetadata missing, reflect-metadata not imported, and decorator ordering issues.
Fix: AWS CloudWatch Logs Not Appearing
How to fix AWS CloudWatch logs not showing up — IAM permissions missing, log group not created, log stream issues, CloudWatch agent misconfiguration, and Lambda log delivery delays.
Fix: Spring Boot "The dependencies of some of the beans in the application context form a cycle"
How to fix Spring Boot circular dependency errors — BeanCurrentlyInCreationException, refactoring to break cycles, @Lazy injection, setter injection, and @PostConstruct patterns.
Fix: Spring Security Returning 403 Forbidden Unexpectedly
How to fix Spring Security 403 Forbidden errors — CSRF token missing, incorrect security configuration, method security blocking requests, and how to debug the Spring Security filter chain.
Fix: MongoDB "not primary" Write Error (Replica Set)
How to fix MongoDB 'not primary' errors when writing to a replica set — read preference misconfiguration, connecting to a secondary, replica set elections, and write concern settings.
Fix: Node.js Crashing with UnhandledPromiseRejection (--unhandled-rejections)
How to fix Node.js UnhandledPromiseRejectionWarning and process crashes — why unhandled promise rejections crash Node.js 15+, how to add global handlers, find the source of the rejection, and fix async error handling.
Fix: Python dataclass Mutable Default Value Error (ValueError / TypeError)
How to fix Python dataclass mutable default errors — why lists, dicts, and sets cannot be default field values, how to use field(default_factory=...), and common dataclass pitfalls with inheritance and ClassVar.
Fix: Python requests.get() Hanging — Timeout Not Working
How to fix Python requests hanging forever — why requests.get() ignores timeout, how to set connect and read timeouts correctly, use session-level timeouts, and handle timeout exceptions properly.