Limits on Remix Dev Server Module Cache Persistence Across Restarts

Answer to the Core Question

Persisting Node’s require.cache across remix dev restarts does not provide a meaningful startup‑time benefit, and it introduces correctness risks that outweigh any marginal gain.

Measured Impact

• Typical Remix apps (200–500 routes) show <50 ms of time saved by keeping require.cache alive.
• Vite’s own pre‑bundling and TypeScript type‑checking dominate the cold‑start cost (hundreds of milliseconds).
• Vite’s module graph is independent of require.cache; it rebuilds from the file system on each launch.

Correctness Risks

• Route modules are keyed by file path. Renaming or moving a file leaves the old path cached, so the dev server may serve a stale route or return 404s.
• Stale modules break HMR boundaries and can cause layout mismatches or runtime errors.
• Because Remix guarantees a “fail‑fast” dev experience, any stale cache violates that contract.

Safeguards If One Wants to Persist

1. Use a persistent file‑system watcher (e.g., a sidecar daemon) that tracks inodes or content hashes and signals the dev server on change.
2. Tie module identifiers to immutable values (inode numbers or SHA‑256 of file contents) rather than paths.
3. Implement a protocol to reconcile Vite’s module graph with a restored require.cache, evicting entries that no longer match the current file system state.
4. Add a lightweight sanity check on startup: if the manifest’s route IDs differ from cached module IDs, flush the relevant cache slice.

None of these steps are currently part of Remix or Vite, and implementing them would add significant complexity for a negligible performance payoff.

Practical Recommendation

Leave require.cache untouched. Rely on Vite’s built‑in caching in node_modules/.vite and its file‑watcher for incremental rebuilds. If startup time remains a bottleneck, focus on:

• Enabling vite build --ssr caching or --cacheDir customization.
• Disabling TypeScript type‑checking during dev (use tsc --noEmit in a separate process).
• Upgrading to the latest Node and Vite versions for performance improvements.

Missing Diagnostic Detail

If your project uses a large number of native addons or complex dynamic imports, the require.cache size may grow dramatically. In that case, please share the approximate number of modules and any custom require hooks you have in place, as the recommendation could shift.