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Read the top exception and every Caused by section. Framework and future wrappers often report where failure surfaced, not its origin. Preserve stack trace, request identifier, runtime version, and safe configuration context. When translating an exception, chain the original cause rather than logging only its message.

Start tracemalloc before the workload, take snapshots at comparable points, and compare line-level allocation differences. It tracks Python-managed allocations, not every native allocation from extensions or system libraries. Correlate it with RSS and object-retention behavior; growing allocation totals do not alone prove a leak if objects are later freed.

Each platform thread consumes native resources, including stack reservation, and excessive runnable threads add scheduling and context-switching overhead. The service may hit native-thread creation errors or degrade before that point. Bound executors, measure queue depth and task latency, and apply backpressure rather than creating one thread per unbounded unit of work.

Read the final exception type/message, locate the failing operation, and inspect the nearest application frame that supplied its input. Reproduce the smallest failing case and trace where that value was created or transformed. Add validation at uncertain boundaries and a regression test; do not catch and suppress the exception at the bottom of the stack.