asyncio internals, GIL, typing tricks, Rust extensions
100 lessons across 6 modules: concurrency & async internals, CPython internals & performance, metaclasses + descriptors + dunder magic, memory + profiling + optimization (memray/tracemalloc), and architecture + code review + senior judgment.
Promotion from mid → senior at a real engineering org. Not 'I read Fluent Python once' — actually defending architecture decisions in front of staff engineers.
Yes — GIL, reference counting, GC, the eval loop, how `import` actually works. Includes free-threading (3.13+) since that's the topic interviewers will ask in 2026.
Both. You build a mini-ORM from scratch using descriptors. Theoretical chapters end with 'here's where this shows up in real code'.
System Design is about boxes and arrows at scale. Senior Deep-Dives is about the code inside the boxes — async internals, perf profiling, code review judgment, ADR writing.
Helps. The 'Architecture + Code Review' module is the closest thing to a staff-engineer practice rig you'll find online — RFCs, ADRs, technical mentoring patterns.
All 101 lessons unlock for $12/month or $89/year. 7-day free trial — card required, cancel in 1 click anytime in Settings.
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