Consistency models

Aerospike supports two consistency models: AP (Available, Partition-tolerant) and SC (Strong Consistency). Understanding when to use each is critical for your application.

AP mode (default)

Available, Partition-tolerant — Prioritizes availability over consistency.

Reads always succeed if any replica is reachable
Writes succeed if any replica accepts them
During network partitions, both sides remain writable
Conflicts resolved by “last write wins” (LWW)

Best for: Session stores, caches, real-time analytics, high-availability requirements.

SC mode (strong consistency)

Strong Consistency — Prioritizes consistency over availability.

Reads return the most recent committed write
Writes require a majority of replicas (quorum)
During partitions, minority side becomes read-only
No conflict resolution needed (linearizable)

Best for: Financial transactions, inventory systems, any “single source of truth” requirement.

Choosing a consistency model

Factor	AP Mode	SC Mode
Availability	Higher	Lower during partitions
Read latency	Lower	Slightly higher
Write durability	Eventually consistent	Immediately consistent
Conflict handling	Automatic (LWW)	Not needed
Use case	Caching, sessions	Transactions, inventory

// AP mode (default behavior)
Session apSession = cluster.createSession(Behavior.DEFAULT);

// SC mode (requires SC namespace on server)
Behavior scBehavior = Behavior.DEFAULT.deriveWithChanges("STRICTLY_CONSISTENT", b -> {});
Session scSession = cluster.createSession(scBehavior);

# AP mode (default behavior)
ap_session = cluster.create_session(Behavior.DEFAULT)

# SC mode (requires SC namespace on server)
sc_session = cluster.create_session(Behavior.STRICTLY_CONSISTENT)

Server configuration

SC mode requires namespace configuration on the server:

namespace myns {
    strong-consistency true
    ...
}