Designing fault-tolerant services that scale horizontally across regions. Replication, consensus, and graceful degradation as first-class concerns.
Encoding invariants in the type system so the compiler refuses incorrect programs. Strong typing as a tool for clarity, not ceremony.
Profiling, measuring, and tuning hot paths until latency disappears. Caches, memory layout, and instruction-level reasoning when it matters.
Implementing primitives correctly: constant-time operations, careful key management, and threat models that survive contact with reality.
Tracing, metrics, and structured logs that make production legible. Building the instruments before you need to read them.
Parsing, lowering, and code generation explored end-to-end. Understanding how source becomes silicon, one IR at a time.