Curriculum

Backend Depth

Closing the gap between "can build it" and "knows why it behaves this way under concurrency and failure." See MISSION.md for the full why.

Lessons

#	Lesson	Reference
1	Why three indexes still weren't enough	Indexing cheat sheet
2	The balance transfer that goes negative	Isolation cheat sheet
3	When the cache expires and the DB falls over	Caching cheat sheet
4	Connection reuse and RTT cost	Networking cheat sheet
5	Blocking I/O and the scheduler	OS cheat sheet
6	The GIL and concurrency models	Concurrency cheat sheet
7	Retries and partial failure	Failure models cheat sheet
8	Why the table grows forever even though you're deleting rows	Isolation cheat sheet
9	Why Postgres ignored your index and scanned the whole table	Indexing cheat sheet
10	Why throughput collapses when the link saturates	Networking cheat sheet
11	Why the server says 90% memory used and nothing is leaking	OS cheat sheet
12	How one thread handles 10,000 connections	Concurrency cheat sheet
13	Why the queue that never fills up will eventually kill you	Failure models cheat sheet
14	How to retry a payment without charging twice	Failure models cheat sheet
15	Why your own write is missing when you read from a replica	Failure models cheat sheet

Other

RESOURCES.md — primary sources and communities, by topic
Learning record: baseline assessment
Learning record: second pass plan (Lessons 8–15)

Start at Lesson 1, go in order. Ask follow-up questions on anything unclear — that's the point.