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External Sources

A secondary database can be backed by an external source. Rather than accepting transactions from clients, it subscribes to an upstream feed and records what it reads as XTDB transactions.

The database is then a read-only mirror of that upstream — it rejects writes from the Postgres wire-compatible server and the Flight SQL server, and tracks the upstream as it changes.

Postgres

Change-data-capture from a Postgres database — see Postgres External Source.

Kafka Connect

Records from a Kafka Connect topic — see Kafka Connect External Source.

An external source is set up when you attach the secondary database: add an externalSource: entry to the ATTACH DATABASE config, alongside its log: and storage:.

See each source’s setup guide for the specifics.