MEPX
Chapter 2 of 10All chapters
  1. 1Start with numbers
  2. 2Tiers and statelessness
  3. 3Scaling
  4. 4Caching
  5. 5Data at scale
  6. 6Queues and async work
  7. 7Consistency
  8. 8Designing for failure
  9. 9Knowing what is happening
  10. 10Making the trade-off

Chapter 2 of 10

Tiers and statelessness

Separating the layers.

The classic split

Clients talk to stateless application servers, which talk to stateful data stores. Keeping state out of the application tier is what lets you add and remove servers freely.

  • Sessions belong in a shared store or a signed token, not in server memory.
  • Any request should be servable by any instance.

Why it matters

Stateless servers make rolling deployments, autoscaling and crash recovery routine instead of dramatic.