High Availability: Designing for Zero Downtime
Master the art of building vector systems that never go down. Learn about Multi-AZ deployment and health-check orchestration.
High Availability: Designing for Zero Downtime
In a production environment, "Oops, the database is down" is not an option. High Availability (HA) is the architectural practice of ensuring your vector service remains reachable even if an entire data center loses power.
In this lesson, we learn how to design a "Self-Healing" vector stack.
1. Multi-AZ (Availability Zone) Deployment
The foundation of HA is geographic diversity. You should never put all your shards in the same "Availability Zone."
- The Strategy:
- Shard 1-Primary:
us-east-1a - Shard 1-Replica:
us-east-1b - Coordinator Node:
us-east-1c
- Shard 1-Primary:
If Amazon's 1a data center goes offline, the system automatically promotes the replica in 1b to Primary, and your users never notice a gap.
2. Health Checks and Failover
Your load balancer must constantly "Ping" your vector nodes to ensure they are healthy.
- State: Healthy: Node continues to receive query traffic.
- State: Unhealthy: Node is automatically removed from the rotation. A new instance is spun up to replace it.
3. The "Read-Only" Fallback Pattern
If your Primary node (the writer) goes down, you might lose the ability to add new documents for a few minutes.
Smart Architecture: Configure your app to switch to a Read-Only mode. The agent can still "Recall" past memories from the replicas, even if it can't "Store" new ones right now. This is much better than a total app crash.
4. Visualizing HA Architecture
graph TD
LB[Load Balancer] --> C1[Coordinator 1: AZ-A]
LB --> C2[Coordinator 2: AZ-B]
C1 --> SA1[Shard 1: AZ-A]
C1 --> SB2[Shard 2: AZ-B]
C2 --> SB1[Shard 1: AZ-B]
C2 --> SA2[Shard 2: AZ-A]
5. Summary and Key Takeaways
- Redundancy is Everything: If you have 1 of anything, you have a Single Point of Failure (SPOF).
- Geographic Diversity: Use multiple Availability Zones (AZs) to survive infrastructure failures.
- Failover Logic: Your database engine (or managed provider) should handle "Leader Election" automatically.
- Graceful Degradation: Design your AI app to function (as read-only) if the write-layer is temporarily down.
In the final lesson of this module, we’ll look at the "Big Reset": Disaster Recovery.