STORAGE PROVIDERS

Choose your
storage.

Keep a consistent document API.
Choose storage based on persistence, sharing, and query needs.

Provider behavior at a glance
Capability	Memory	FileSystem	Redis	PostgreSQL
Documents live in	Process memory	Memory + JSON file	Redis	PostgreSQL
Persistence	Temporary	Periodic save (~5s)	Write-through¹	Committed writes
Shared across instances	No	No	Yes	Yes
Index lifetime	Until unload	Rebuilt on reload	Persisted in Redis	Persisted in PostgreSQL
Atomic batches	Yes	Yes, saved immediately	Yes	Yes

¹ Redis persistence and eviction configuration determine durability. FileSystem uses one database owner per file; call Save() to flush explicitly.

01 / IN PROCESS

Memory

For temporary data, tests, and applications that don’t need storage to survive a restart. No external service to configure.

Package on NuGet ↗

dotnet add package Soenneker.Librarian.Memory

using Soenneker.Librarian.Memory.Registrars;

builder.Services.AddMemoryLibrarianDatabaseAsSingleton();

Scoped registrations are also available. A scoped memory database owns its own data.

02 / LOCAL JSON

FileSystem

In-memory access with a JSON file behind it. Designed for a single database owner, with periodic saves and immediate persistence for atomic batches.

Await database.Save() for an explicit flush. Dispose the database’s owner asynchronously to complete shutdown persistence.

dotnet add package Soenneker.Librarian.FileSystem

using Soenneker.Librarian.FileSystem.Registrars;

builder.Services.AddFileSystemLibrarianDatabaseAsSingleton();

{
  "Librarian": {
    "FileSystem": { "FilePath": "data/librarian.json" }
  }
}

03 / SHARED STORAGE

Redis

Shared documents and persisted indexes for multiple application instances. Reads fetch current Redis data; writes update documents and indexes together.

No RedisJSON, Redis Search, or Lua required. Use a non-evicting database; cluster deployments require Redis 8 or later.

Redis setup & guarantees ↗

dotnet add package Soenneker.Librarian.Redis

using Soenneker.Librarian.Redis.Registrars;

builder.Services.AddRedisLibrarianDatabaseAsSingleton();

{
  "Azure": { "Redis": { "ConnectionString": "localhost:6379" } },
  "Librarian": {
    "Redis": { "Key": "my-app:librarian" }
  }
}

04 / PERSISTENT SQL

PostgreSQL

Shared persistent documents with SQL-backed filtering, sorting, paging, and aggregates. Writes and conditional batches commit immediately.

Indexes persist across restarts. Requires PostgreSQL 16 or later. Supply connection credentials through your application’s secret configuration.

PostgreSQL setup & queries ↗

dotnet add package Soenneker.Librarian.Postgres

using Soenneker.Librarian.Postgres.Registrars;

builder.Services.AddPostgresLibrarianDatabaseAsSingleton();

Configure Librarian:Postgres:ConnectionString and Librarian:Postgres:Key.

Same API. Know the differences.

Memory and FileSystem can fall back to local evaluation for unsupported queries. Redis and PostgreSQL throw NotSupportedException. Review query support before moving a workload between providers.

Compare query capabilities ↗