Choosing storage

Storage choice has two dimensions: the provider holds records; the topology decides whether memory or that provider is authoritative.

Topology	Authority	Processes	Durability	Use for
InMemory	Process memory	One	None	Unit tests, local demos, disposable work.
SingleServer	Memory with synchronous durable replica	Exactly one	Durable restart recovery	Low-latency single-instance services.
Distributed	Durable provider	One or more	Durable coordination	Scale-out and high availability.

Calling a durable provider selects single-server mode unless you explicitly call UseDistributed(). UseRedis always selects distributed mode. Never point two processes at the same single-server replica: each believes its private memory is authoritative and drift detection will fail.

Capability matrix

Provider	Queue	Recurring	Graph	Fair groups	Topologies
In-memory	✓	✓	✓	✓	In-memory only
EF Core SQL	✓	✓	✓	✓	Single-server, distributed
LinqToDB SQL	✓	✓	✓	✓	Single-server, distributed
Redis	✓	✓	—	—	Distributed

Queue capability includes ordinary scheduling, execution history and job monitoring. Recurring adds durable schedule reconciliation/materialization. Graph adds atomic batches, dependencies, continuations and batch monitoring. The dashboard hides or returns 404 for unsupported graph views.

Tradeoffs

• In-memory is fastest and deterministic, but a restart loses pending jobs and history.
• Single-server acquires from memory and writes every transition to a full-capability SQL replica. Startup restores the durable snapshot. It cannot provide multi-process failover.
• Distributed SQL coordinates leases, recurring schedules, graph transitions and fair-group cursors in the database and is the full-featured scale-out option.
• Redis offers efficient distributed queues and recurring work, but not batches, continuations or fair-group acquisition.

A custom provider

Implement IJobStorage for queue capability. Add IRecurringJobStorage and/or IJobGraphStorage only when their atomicity contracts are honored. Implement IJobStorageReplica as well to qualify for single-server mode. Providers must initialize idempotently, claim due work atomically, enforce worker ownership and leases, make recurring materialization unique, paginate monitoring, tolerate repeated async disposal, and make graph commit/release/cascade transitions atomic. See the compact contract map in API reference.