Scaling and Performance

What is inside

The full table of contents. Nothing here is hidden: if a section you need is not in this list, the notebook is not the right one and you should not spend a week on it.

1. 1. "Slow" is not a bug report
2. 2. Latency is a distribution, not a number
3. 3. Why P99 is your most valuable customers
4. 4. Throughput, and the curve that bends
5. 5. Utilization and the knee
6. 6. Headroom, and why traffic arrives in bursts
7. 7. Never guess. The week spent on the wrong fix
8. 8. Profiling, and what a flame graph shows
9. 9. Distributed tracing, and why waiting needs it
10. 10. What to measure, in what order
11. 11. N+1: the shape, not the name
12. 12. Indexes: the catalogue, the tree, and the cost
13. 13. Composite and covering indexes
14. 14. EXPLAIN ANALYZE: deciding instead of guessing
15. 15. Connections are not free
16. 16. Pooling, and the autoscaler that killed the database
17. 17. What caching actually buys
18. 18. Invalidation: the second hard problem
19. 19. Where the cache lives
20. 20. Three patterns: aside, through, behind
21. 21. Hit rate, and the four things that move it
22. 22. Vertical scaling, and its three ceilings
23. 23. Horizontal scaling, and the bill it comes with
24. 24. Statelessness is the price of admission
25. 25. The load balancer, and five algorithms
26. 26. Health checks, and the server that is up but dead
27. 27. Read replicas
28. 28. Replication lag, and the read-after-write bug
29. 29. Sharding, and the key that is hard to choose
30. 30. Distributed databases: rent, do not build
31. 31. The speed of light, and the latency budget
32. 32. CDNs: what goes on one
33. 33. The edge, and what it cannot do
34. 34. Asynchronous processing: the queue as a latency tool
35. 35. What can be made async, and what cannot
36. 36. Microservices scale teams, not machines
37. 37. What a network boundary costs
38. 38. Serverless: the pricing model is the point
39. 39. Cold starts, limits, and statelessness
40. 40. When serverless fits, and when it does not
41. 41. How to answer "how would you scale this?"
42. 42. Five traps
43. 43. The five rules
44. Appendix A. Numbers worth memorising
45. Appendix B. Glossary
46. Appendix C. Final review

How to read it

Read with a pen. Every notebook opens with a question to answer before you start and asks you to redo the answer at the end, and the margin in the Print edition exists so you have somewhere to be wrong first. The Tablet edition is 16:9 with vector text, so note apps draw on it rather than treating it as a photograph.