Field Notes

Guides we share with clients before instrumentation week. Written for working Python maintainers, not beginners learning syntax.

Reading cProfile output without drowning in rows

8 min read · Updated March 2026

Sort keys, cumulative vs total time, and when to ignore functions that are merely transit points for the GIL.

When to profile before you rewrite a module

6 min read

Rewrite urges often follow a bad deploy, not a bad design. A short decision tree for tech leads.

Memory growth in long-running Python workers

10 min read

How we tell a leak from a cache that never evicts, using tracemalloc snapshots taken hours apart.