In payment gateway systems, the transaction table often grows rapidly, leading to performance bottlenecks. One effective way to scale a transactional database is sharding — splitting the database into smaller, more manageable pieces based on a shard key. In this guide we will walk through the process of sharding an existing transaction table in PostgreSQL, explaining key considerations, risks, and two popular sharding approaches: row-based and table-based . Key Considerations and Risks Before diving into the implementation of sharding, it’s important to understand the key considerations and risks associated with this approach: Considerations: Sharding Key : The selection of a shard key is crucial. A good shard key ensures even distribution of data, while also aligning with the most frequent query patterns. For payment transactions, transaction_date or customer_id can be used. Database Complexity : Sharding increases the complexi...