ARC 6Prove Boundaries and DeliverChapters 23–26
Arc 6 Recap — Graduate with Boundaries and Evidence (Chapters 23–26)
DSM provides explicit semantics, recovery paths, and evidence boundaries for suitable shared coordination state. The corresponding systems remain authoritative for business facts.
Four graduation decisions
- Protocol: real ports prove reachability; Redis-shaped is not a Redis product and does not change partition semantics.
- Scope: federation preserves different contracts for three collections and creates neither a global transaction nor cross-region Lease ownership.
- Exclusion: authoritative facts, complete history, strong coordination, and pure cache return to systems fitted to those duties.
- Release: evidence level follows the claim and separates current green results from deployment acceptance.
How this arc realizes DSM's value
Real ports, federation, technology exclusion, and the capstone test the limits of DSM's value. The team can name consistency work reused from DSM, business/production responsibilities remaining outside, and the next decision: adopt, reject, or validate further.
Final mapping of the running case
| State | Final choice | External responsibility retained |
|---|---|---|
| route hint | Register | health authority, TTL/cleanup, bad-route handling |
| shard owner | Lease | external fencing, uncertainty, partition policy |
| request counter | PN-Counter | mergeable observation only, no settlement |
| order and inventory | reject DSM as authority | transaction, audit, compensation |
| cross-region coordination | federation selected per collection | real relay, security, capacity, recovery |
Verifiable learning outcomes
- Select Register, Lease, CRDT, or rejection from a business invariant.
- Explain the difference among local commit, remote visibility, repair, and business success.
- Locate problems with diagnostics/metrics/trace while controlling metric cardinality.
- State honest security, lifecycle, capacity, and federation boundaries.
- Run the capstone while keeping book evidence separate from target deployment acceptance.
Final sentence
Distributed shared memory does not disguise remote access as local access. DSM gives inevitable divergence explicit collection semantics, recovery processes, and evidence boundaries so business teams can understand it, engineering systems can handle it, and experiments can verify it.