Angular 20 Migration: SSR Challenges & Resolutions with Vite, ESM, and Express 5

A real-world account of migrating Halodoc's Angular SSR monolith to Angular 20, covering 12 specific challenges and their resolutions. Key changes include: switching from Webpack to Vite+esbuild (56% faster builds), migrating from CommonJS to ESM (.mjs output), replacing CommonEngine with AngularNodeAppEngine, upgrading from

#webdev

#nodejs

#angular

#vite

Feb 20•12m read time•From blogs.halodoc.io

Table of contents

1. Build System Migration — Webpack → Vite + esbuild 2. SSR Configuration — The Missing Metadata Problem 3. CommonJS → ESM — The Ripple Effect 4. Express 4 → Express 5 — Route Syntax Rewrite 5. Dependency Compatibility — Three Gotchas 6. CommonEngine → AngularNodeAppEngine 7. Strict Package Export Enforcement 8. Route Extraction Errors — Catch Block Strictness 9. CSP Nonce Injection — Security Under SSR 10. Prometheus Monitoring — Singleton Registry Pattern 11. Missing Type Declarations — Custom .d.ts Files 12. Removed Dev Server Flags Migration Quick-Reference Checklist Conclusion References Join us Tags