An admin updates a product title in the database, but Elasticsearch still shows the old title for two minutes. A customer searches the new title and gets zero results. How do you design indexing and consistency for this?

SearchElasticsearchEventual ConsistencyIndexing

How I frame it

Search is a derived read model. DB is source of truth; ES lags. Design for bounded staleness, reliable indexing, and UX that does not promise instantaneous global search after every admin save.

Indexing pipeline

Transactional outbox on product update → ProductChanged(id, version) to Kafka.
Indexer consumer: Load latest row by id (or embed payload), index / update ES doc with external_version = DB version — ignore stale events.
CDC (Debezium) as alternative to app outbox — same consumer pattern.
Refresh policy: Prefer near-real-time (refresh_interval 1s) for catalog; do not block admin HTTP on ES refresh unless "preview search" is required.

Admin: title "Galaxy Buds" → "Galaxy Buds Pro" (version 44)
  Outbox → Kafka → Indexer → ES doc version 44
Search "Buds Pro" before index: 0 hits
  Mitigations below

Closing the UX gap

Admin preview: After save, query primary DB / admin API by id — not public search — to confirm edit.
Synchronous index on critical path (optional): Admin "Publish" waits for indexer ack + _refresh for that id — rare, paid for correctness.
Fallback search: If ES miss on exact SKU / id, GET product by id from DB.
Alias swap for big reindex: Blue/green index; never dual half-updated public alias mid-migration.

Weak answer

"Write to ES in the same request as DB." Dual-write drifts on crashes; no versioning. "Just lower refresh_interval to 0." Costly; still eventual if indexer is behind.

Follow-up questions

Indexer lag of 10 minutes — alert?

Yes — consumer lag + "age of oldest unindexed outbox row" SLO. Page when search SLO burn threatens launch windows.

Partial updates / nested variants?

Index denormalized product document; version whole doc. Partial ES update scripts only with care for lost updates.

Delete product?

Outbox ProductDeleted → ES delete by id; idempotent. Tombstone if consumers reorder.