Cockroach Labs’ architecture deep dive (Sep 15) for Continuum — elastic multi-tenant CRDB estate. Design spine: Plenum disaggregated storage (Pebble → shared object store; Range Shared LSM so new KV nodes get metadata links, not full copies; AZ-spread NVMe blob servers + S3 backstop); nearly-stateless tenant-keyed KV; SQL Pods that scale 0→N per Virtual Cluster with mTLS isolation; Slots + Tokens admission plus Resource Manager fairness; RoachMgr control plane with a Paxos-elected coordinator as a separate failure domain from CRDB Raft. Skim Aegis / Migration Assistant product wrap.

Meta open-sources Rebalancer (Sep 21) — the assignment library used internally for 9+ years. Spec language separates objects / bins / constraints / objectives from solvers: dimensions, partitions, scopes, utilization → expression DAG → either MIP (Xpress/Gurobi/HiGHS) or heavily parallelized local search. Production: Shard Manager, RAS, Taiji, serverless locality, ML training balance. Scale: ~40M assignment problems/day; P99 ~12s at 265k objects / 3.2k bins. Ships with Rebalancer Explorer for binding-constraint debugging. OSDI’24 pedigree; Apache-2.0.

Stripe’s Document DB fleet (~2,000 MongoDB shards, 40+ layouts) outgrew hard-coded single-step remediation plugins. Reframe: model shard health as a directed state graph; search from ground reality → Source of Truth. BFS first, then Dijkstra with edgeWeight = misconfiguration × estimatedTime so the planner minimizes time spent misconfigured and can return partial remediation. Go CommonContext abstracts Temporal — same business logic for in-memory simulation or durable workflows. Claims: ~30% fewer pages / 12 unhealthy-shard days/yr; zero code for new layouts.