Instruction file imported from GoranErhartic/cursor-development-rules (.cursor/rules/languages/aws-lambda/code-quality.mdc). Copyright stays with the author.

Lambda Code Quality

Structure

• functions/ — one folder per Lambda (handler.ts, schema.ts); services/ — business logic; repositories/ — data access; shared/ — clients, errors, middleware, logger, types; test/ — setup, factories
• cdk/ — bin, lib/stacks, lib/constructs

TypeScript

• Target ES2022; module: "NodeNext", moduleResolution: "NodeNext"; strict, noUncheckedIndexedAccess, paths for @/*
• Lambda-specific tsconfig: include only src (or functions) for build; exclude cdk from function bundle

Bundling (esbuild)

• Use Node 22 target; externalize AWS SDK v3 and optional dependencies to reduce bundle size; single entry per function
• Minimize dependencies in function package; tree-shake; check bundle size in CI

ESLint

• Use flat config (eslint.config.mjs); TypeScript and Lambda best practices; no unused vars; consistent imports

Conventions

• Small bundles; strict TypeScript; single responsibility per function; shared code in shared/; no secrets in code

Anti-Patterns

• Large transitive dependencies; bundling cdk; non-strict TS; duplicated logic across functions

See also: lambda-handlers.mdc, cdk-infrastructure-lambda.mdc, languages/nodejs/code-quality.mdc