Storage Backends Overview

LongCache separates vector similarity search (handled by FAISS) from payload and metadata persistence (handled by pluggable backends).

Supported Backends

Backend	Persistence	Multi-Process / Cluster	Setup Required	Best For
SQLite (Default)	Disk	Single-node / Thread-safe	None (Automatic)	CLI tools, local apps, single containers
Redis	In-Memory / AOF	One LongCache process per cache	Redis service	Shared response persistence with a local index
Memory	None (RAM)	Single Process	None	Unit tests, CI/CD, ephemeral workers

All FAISS indexes are local to the LongCache process. Redis response storage does not synchronize those indexes between workers. backend="async_redis" is rejected by LongCache in v0.1.1; the standalone async backend remains experimental.

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Configuring the Backend

The backend is configured via CacheConfig:

from longcache import LongCache, CacheConfig

# 1. SQLite (default)
cache_sqlite = LongCache(CacheConfig(backend="sqlite", db_path=".longcache/cache.db"))

# 2. Redis
cache_redis = LongCache(CacheConfig(backend="redis", redis_url="redis://localhost:6379/0"))

# 3. Memory
cache_memory = LongCache(CacheConfig(backend="memory"))