Assess students' ability to design a Byzantine fault‑tolerant, sharded consensus protocol for geo‑distributed key‑value stores. Specify system model and assumptions (network synchronicity, cryptographic primitives, fault bounds), propose shard assignment and dynamic membership/reconfiguration mechanisms, design an intra‑shard BFT consensus algorithm (e.g., PBFT/HotStuff variant) and a safe, efficient cross‑shard transaction protocol ensuring atomicity and consistency. Address view change, leader election, quorum selection, state transfer, recovery, and defenses against Byzantine behaviors. Optimize for geo‑latency, throughput, and minimal cross‑region communication; analyze correctness (safety/liveness proofs under stated faults), message and latency complexity, storage/replication overhead, and tradeoffs. Deliver a protocol specification, correctness arguments, complexity analysis, and an experimental evaluation plan including benchmarks and adversarial scenarios.