content-hash-cache-pattern

Caching expensive file processing results uses SHA-256 content hashes as cache keys, preventing redundant computations by retrieving previously computed analysis for identical files. Cache entries are stored in file-based JSON for persistence across sessions.

Content-based caching uses SHA-256 hashes of file content rather than file paths, ensuring cache hits even if files are renamed or moved. This path-independent retrieval matches identical content regardless of its location in the file system.

Cached file processing data becomes invalid automatically when the underlying file content changes. Because the cache key is a SHA-256 content hash, any modification to the document produces a new hash, bypassing the old cache entry.

The best way to keep core processing functions pure while adding caching logic is through service layer separation. A separate wrapper function handles the SHA-256 hashing and cache retrieval, keeping the underlying processing logic unmodified.

You can use content hash caching for batch processing documents like PDFs, images, and text files. If the same document is encountered again during the batch, its previously computed analysis is reused, saving significant processing time.

You need frozen dataclasses for cache entries and file-based JSON storage for cache persistence when using this content hashing approach. These structures ensure immutable cache records and reliable retrieval of expensive file processing results.