Offline connectivity, queue, snapshot, and recovery checks

Choose the guarantee actually supplied by each data structure. Keep batch knowledge, in-process visibility, and durable recovery separate.

Lessons

• Offline connectivity: edge lifetimes and rollback unions
• Bounded queues: close, wake waiters, and drain accepted work
• Index snapshots: publish related maps as one in-memory version
• Page journals: replay committed index changes

Design exercise

• Project: plan a reversible depot release
• Data Structures