TypeScript Best Practices for Large-Scale Web Applications

TypeScript adoption has crossed the tipping point. Most serious web applications being built in the US market today start with TypeScript, not JavaScript. The question is no longer "should we use TypeScript" but "are we using it well." After working on large-scale TypeScript codebases, SaaS platforms, FinTech APIs and healthcare applications, the patterns that separate a maintainable codebase from a messy one are consistent. Here's what actually matters at scale. 1. Stop Using any . Use unknown Instead any is TypeScript's escape hatch, and like all escape hatches it gets overused. The problem: any disables type checking entirely. You get none of TypeScript's safety guarantees on that value or anything it touches. unknown is the type-safe alternative. It forces you to narrow the type before using it: // Bad: any disables all type checking downstream function parseConfig ( raw : any ) { return raw . database . host ; // No error, but crashes if shape is wrong } // Good: unknown forces yo