Fedify: an ActivityPub server framework
Since #Fedify v0.12.0, when verifying HTTP Signatures or Object Integrity Proofs, it will cache the public keys once fetched. It is okay even if a cached key becomes outdated because a verification failure due to a cached key will invalidate the cache and force a verification retry.
This feature is available for preview in v0.12.0-dev.307+235629d5 (JSR or npm).