Multi-AZ redundancy

What you'll be able to do

1. 1Explain why every tier — load balancer, servers, database — must span independent zones, and what a zone failure does to a tier left in one zone.
2. 2Predict whether the zones left after a failure can carry the load, from how many zones there are and how busy each one runs before the loss.
3. 3Choose how many zones to run, how much spare capacity to keep in each, and whether to keep traffic inside a zone or spread it across zones.

Inside the lesson

steps

11

questions

13

simulations

4

You guess first, then run the system and see if you were right.

More on the Resilience Line

1. Failure modes and availabilityOpen9 min
2. Timeouts — capping the waitMembers9 min
3. Retries — with backoff and jitterMembers12 min
4. Circuit breakerMembers10 min
5. Bulkhead — walls between workloadsMembers12 min
6. Load shedding — turning the excess awayMembers12 min
7. Backpressure — a queue that says noMembers11 min
8. Rate limiting — a budget for each callerMembers12 min