| remove required field | old-reader failure | deprecate, observe, then remove |
| reuse field meaning | silent corruption | create a new field |
| registry outage on hot path | consumer outage | bounded schema cache |
| latest-only test | replay failure | transitive history test |
| unbounded quarantine | hidden data loss | alert and governed replay |
| Track incompatible submissions, unknown IDs, deserialize failures, schema-cache misses, and consumer-version distribution. | | |
| ## Test yourself | | |
| 1. Why is semantic compatibility harder than syntax? | | |
| 2. How can caching survive registry outage? | | |
| 3. What proves a field is safe to remove? | | |
Continue to professional.md. | | |