Comment by whispem

Thank you for this sharp and detailed question! In minikv, both Raft and 2PC are purposefully implemented, which may seem “overkill” in some contexts, but it serves both education and production-grade guarantees:

- Raft is used for intra-shard strong consistency: within each "virtual shard" (256 in total), data and metadata are replicated via Raft (with leader election and log replication), not just for cluster membership;

- 2PC (Two-Phase Commit) is only used when a transaction spans multiple shards: this allows atomic, distributed writes across multiple partitions. Raft alone is not enough for atomicity here, hence the 2PC overlay;

- The design aims to illustrate real-world distributed transaction tradeoffs, not just basic data replication. It helps understand what you gain and lose with a layered model versus simpler replication like chain replication (which, as you noted, is more common for the data path in some object stores).

So yes, in a pure object store, consensus for data replication is often skipped in favor of lighter-weight methods. Here, the explicit Raft+2PC combo is an architectural choice for anyone learning, experimenting, or wanting strong, multi-shard atomicity. In a production system focused only on throughput or simple durability, some of this could absolutely be streamlined.