The document discusses the challenges and strategies in building robust applications capable of handling heavy web traffic and potential failures. It emphasizes the importance of strategies such as load testing, queue decoupling, and healthy logging for system recovery and stability. The overall message revolves around viewing failures as opportunities for improvement and implementing defensive coding practices.

1. Call Me Never
Building apps that don't wake you up
David Dossot

2. Great in movies ...
... Tough in real life.

3. 5 million visits a day...
... And counting.

4. Aiming for five nines...
... And 100x traffic

5. Readiness
Degradation
Recovery
Strengthening
99.9962
( °□°╯ ）╯︵ ┻━┻

6. Load test and profiling
Readiness

7. Readiness
Replay access logs

8. Readiness
Welcome to the Internet
GET /admin.php
GET /catalog/compare/?action=DELETE_FROM_COMPARE
_RESULT&IBLOCK_ID=3
Host: -- DROP DATABASE users;

9. Degradation
Decouple with queues and topics

10. Degradation
Delay, don't fall down

11. Degradation
Short circuit blocking-IOs

12. cache.get(key)
Degradation
Beware of benign code

13. Recovery
Self heal from transient failures

14. Recovery
Self heal from transient failures

15. Recovery
Maintain stable state

16. Recovery
Replay stable state

17. Strengthening
Healthy health checks

18. Strengthening
Healthy health checks

19. Strengthening
Code defensively and log abundantly
try {
// risky stuff
} catch {
// useful log
}

20. Strengthening
Failure is opportunity for more tests