Lifecycle rules are the first feature that makes momo delete data on a schedule rather than on request — which turns age, storage class, and delete markers into correctness problems. This post walks through the expiration and transition engine, why a background worker is the only safe place to run it, and how expiration composes with versioning’s delete markers.
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.
Verify-on-read re-hashes the full object on every local read (~8x slower than write). A ReadVerifier seam skips re-verification for blobs verified this process, while scrub still catches bitrot.
Phase-0 profiling harness via go test -cpuprofile/-memprofile; Rule 75 forbids networked pprof on unauthenticated listeners. The baseline proved stdlib SHA-256 already uses AVX2.
Adaptive behaviors use compile-time Go interface seams injected at decision points — not dynamic plugins. The fast path stays concrete; the trust core stays auditable; policy is declarative.
R5 Phases 2-4 shipped: storage metrics (disk, CAS, GC), P2P metrics (SWIM, leases, scatter-gather), and opt-in latency histograms — all with <1% overhead via sync/atomic counters.
Final 501 sweep: SelectObjectContent, UploadPartCopy, analytics, inventory, metrics, intelligent-tiering now return honest 501 NotImplemented.
5 object-level query parameters now return honest 501 NotImplemented instead of silently falling into GetObject/PutObject/DeleteObject.
16 bucket config subresources (versioning, ACL, policy, CORS, lifecycle, etc.) now return honest 501 NotImplemented instead of silently misrouting to ListObjects/GetObject.