How to Refactor a Bloated Next.js Middleware File Using the NEMO Pattern

Next.js middleware files often start simple but grow unwieldy as redirects, locale handling, authentication, and security headers accumulate in a single file. The core problem is mixed responsibility, where unrelated logic coexists without a clear execution order, making changes risky and hard to test. A practical solution involves splitting middleware into discrete rules, each handling one concern, arranged in an explicit priority sequence. The NEMO library formalizes this composition pattern, treating middleware as an ordered set of independent proxy rules rather than a chain of nested conditionals. Keeping internal paths like static assets and health checks at the top of the rule list reduces unnecessary processing and prevents unintended side effects.