Why should you care?

Flipkart API tier opening 5000 connections would crash postgres — pool 50 and reuse; batch INSERT cuts round trips.

See it live — copy this example

Run in pgAdmin or psql.

-- Batch insert pattern (run from psql simulating app batch)
INSERT INTO order_items (order_id, product_id, line_total)
SELECT 9001, product_id, price
FROM products
WHERE product_id = ANY(ARRAY[1,2,3]);

What happened?

• Single INSERT...SELECT loads multiple line items from product prices — one round trip vs three separate INSERTs from app loop.
• Follow the steps below — typing the code yourself is the fastest way to learn.

Practice next

1. Time loop of 100 single INSERTs vs one INSERT SELECT.
2. Enable pg_stat_statements and find top calls by total_time.
3. Configure app pool max size below max_connections.
4. Use COPY FROM STDIN for 10k staging rows.
5. Compare extended query protocol prepared statement in driver docs.

Remember

Pool connections; keep transactions short. Batch writes and use COPY for bulk load. Keyset pagination beats OFFSET at depth.

PostgresVerse cart checkout

Checkout refactored from 15 queries to 3 with batch line insert and single balance UPDATE.

Outcome: Checkout latency halves during sale event.