Programming Tutorials

  It’s the distributed system nightmare every backend engineer encounters eventually. Your application successfully commits a record to the database (e.g., a new user sign-up). Immediately after, it attempts to publish an event to Apache Kafka to trigger downstream services (e.g., send a welcome email). But the network blips. The message broker is unreachable. The application throws an error, but the database transaction is already committed. You now have a  dual-write inconsistency . The user exists in your primary database, but the rest of your microservices architecture has no idea. The system is out of sync, and manual reconciliation is painful. This guide details how to solve this strictly using the  Transactional Outbox Pattern  with PostgreSQL, Kafka, and Debezium. The Anatomy of the Dual-Write Problem Before fixing it, we must understand why the naive approach fails. In a monolithic architecture, you might rely on a single ACID transaction. In microservices, ...

  You have a high-throughput PostgreSQL database. You monitor your disk usage and notice your indexes are growing disproportionately to your table data. Query performance is degrading—specifically, Index Scans are becoming I/O bound. You check   pg_stat_user_tables   and confirm that   autovacuum   is running frequently. The natural assumption is that  autovacuum  handles space reclamation. However, in write-heavy environments—especially those with random-access updates or deletes— autovacuum  often fails to shrink the physical footprint of an index. The index becomes "bloated," containing massive amounts of empty space that the OS filesystem still has to cache or read. Historically, reclaiming this space required  REINDEX , which locks the table against writes—a non-starter for 24/7 production systems. The solution introduced in PostgreSQL 12 (and refined since) is  REINDEX CONCURRENTLY . The Root Cause: MVCC and B-Tree Fragmentation To...