Product

A cache, an executor, and a way to debug both

The cache is the easy part. Explaining a miss is what people actually need.

Cache tiers

Tier	Location	Typical hit rate	p50 latency
In-memory	runner process	31%	0.2 ms
Node proxy	runner host disk	44%	1.8 ms
Regional	same region	18%	18 ms
Origin	primary region	1%	64 ms

Explaining a miss

bash

anvil explain //services/api:image --build 9c31f0a2

action key differs from cached entry:
  input  src/handler.go        sha256:4f2a… → sha256:8c31…
  env    GOFLAGS               '-mod=mod' → '-mod=readonly'
  tool   go                    1.25.0 → 1.25.1

3 differences · 2 are non-hermetic (env, tool)
suggestion: pin toolchain in the workspace to restore hit rate