koa_skill

Overview

This skill is a practical, opinionated guide for building robust, scalable, and secure Node.js applications with the Koa framework. It codifies middleware patterns, operational requirements, context usage, security controls, and routing organization into a concise reference. The goal is to standardize Koa best practices so teams ship reliable APIs faster.

How this skill works

The guide inspects common Koa application layers and prescribes concrete patterns you should adopt: async middleware chaining, explicit context usage, graceful shutdown, health checks, and security middleware. It describes what to declare in middleware, how to manage ctx state and responses, and what operational endpoints and signal handlers to implement. Each recommendation maps to code-level actions you can apply immediately in your app.

When to use it

• Bootstrapping a new Koa service and defining team conventions.
• Auditing an existing Koa app for middleware, security, and shutdown issues.
• Designing API architecture that needs predictable request/response flow.
• Preparing applications for production with health checks and graceful shutdown.
• Onboarding engineers to a shared Koa coding standard.

Best practices

• Declare every middleware as async (ctx, next) and await next() exactly once.
• Use ctx.state to pass data between middleware and avoid global variables.
• Set ctx.status before assigning ctx.body and handle response logic after await next().
• Implement a top-level error listener and a try/catch error-handling middleware to avoid process crashes.
• Add graceful shutdown: stop accepting requests, close DB connections, then exit on SIGTERM/SIGINT.
• Use koa-helmet, signed cookies with secure app.keys, and centralized security headers.

Example use cases

• Create a users API with Router prefixes (e.g., /users) and middleware-auth populating ctx.state.user.
• Add a /health endpoint that returns 200 only when DB connections are healthy for load balancers.
• Refactor legacy middleware to async/await chains to ensure proper request and response ordering.
• Deploy a Koa service with SIGTERM handlers that close the HTTP server and disconnect from the database.
• Standardize cookie handling by signing cookies and configuring secure keys across environments.