content-hash-cache-pattern

Cache expensive file processing results by hashing file content with SHA-256 to produce stable, path-independent cache keys. This approach stores deterministic JSON entries in a file-based cache, automatically invalidating when content changes and preventing redundant computation across runs.

File-processing caches keyed by file path break on moves or renames because the path changes. Using SHA-256 content-hash keys solves this by making the cache path-independent, so the cached results remain valid regardless of where the file is located.

Set up a content-hash cache for PDF parsing and OCR by separating your pure processing function from the caching logic, then wrapping it with a service layer that orchestrates read/write operations and handles cache misses using file-based storage keyed by SHA-256 hashes.

The content-hash cache pattern does not require a specific framework, as it has no dependencies. It requires a file-based cache storage system with deterministic JSON entries and a small service layer to orchestrate read/write operations and handle cache misses.

The best way to auto-invalidate cached text extraction results is to use SHA-256 content hashing for cache keys. Because the hash is derived from the file content itself, any modification to the source file produces a new hash, naturally invalidating the old cache entry.

You should not use a content-hash cache pattern when your processing function cannot be separated into a pure function, or when the overhead of computing SHA-256 hashes for very large files outweighs the computational cost of the file processing itself.