How we eliminated the final per-response heap allocation in S3 XML rendering by swapping time.Format for time.AppendFormat in the ListParts handler. Teaches: the stack-buffer time formatting pattern, why Format allocates, and how microbenchmarks prove the win.

The momofs FUSE mount traded its hand-rolled bazil.org/fuse adapter for the go-fuse/v2 high-level fs API, mapped all 22 node callbacks to go-fuse interfaces, and deprecated consistency=cached.

time.Format allocates a fresh string on every S3 GET/HEAD response. Swapping to time.AppendFormat drops that heap escape to zero — measured 32 B/op saved per request on the hottest read path.

How we optimized S3 XML responses by replacing time.Format with time.AppendFormat to eliminate heap allocations. Teaches: stack-buffer time formatting pattern, hot path identification via pprof.

The FUSE transport (momo -imp fs): bazil.org/fuse binding, per-handle buffered writes, /dev/fuse-gated e2e, and a clean unmount lifecycle.

Base-vs-branch benchmark comparison gates every PR — plus the runner-noise saga (S3PutSpool, LocalWrite, allowlist, apostrophe) that made it honest.

The R4 POSIX core: inodes as content-addressed manifests, files as blobs, atomic rename, hardlinks, permission enforcement — a filesystem on momo.

Ack only what survived: fsync/group-commit durability barrier, survivor quorum, and read-your-writes — the write-side of the P0 stack.

When a local replica is corrupted or missing, degraded read fetches from healthy survivors transparently, while a background rebuild loop restores cluster redundancy.

Replicas must not ride in the same rack: CRUSH weights become rack/zone/DC-aware so a single domain failure can’t lose the data.