The N+1 problem occurs when an application fetches a collection with one query, then issues another query for each item.

Example

• One query fetches 100 orders.
• A separate query fetches the customer for each order.
• The total can be approximately 101 queries.

Why it hurts

• More network round trips and latency.
• Increased database load.
• Performance degrades as collection size grows.

Solutions

• Use a JOIN when a combined result is appropriate.
• Use ORM eager loading or batch fetching where suitable.
• Batch repeated lookups with DataLoader-style approaches in appropriate systems.
• Inspect SQL logs, query counts, and execution plans.
• Avoid joining multiple large one-to-many relationships blindly, as row counts can multiply.