Observe two-phase commit blocking with PREPARE TRANSACTION

Act as a coordinator by hand across two databases, stop between the phases, and watch a prepared transaction keep its locks until it is resolved.

The exercise happens on PostgreSQL documentation + local PostgreSQL. Canonical link: https://www.postgresql.org/docs/current/sql-prepare-transaction.html. Link check: link responded (5 Oct 2026). Opened from this app 0 times; opening is not counted as an attempt.

Supports: Distributed-transaction reasoning for system design and database research interviews.