@Query for custom JPQL in Spring Boot - Performance & Optimization

Performance: @Query for custom JPQL

MEDIUM IMPACT

This affects database query execution time and how quickly data is fetched and rendered on the page.

Fetching filtered data from the database using JPQL

Spring Boot

@Query("SELECT u FROM User u WHERE u.status = :status")
List<User> findUsersByStatus(@Param("status") String status);

Filters data at the database level, reducing data size and speeding up response.

📈 Performance GainReduces data transfer size; lowers LCP by faster query execution.

Fetching filtered data from the database using JPQL

Spring Boot

@Query("SELECT u FROM User u")
List<User> findAllUsers();

Fetching all users without filtering causes large data transfer and slow response.

📉 Performance CostBlocks rendering until full data loads; increases LCP time significantly.

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Fetching all data without filters	N/A (server-side)	N/A	High due to large data	[X] Bad
Fetching filtered data with JPQL @Query	N/A (server-side)	N/A	Lower due to smaller data	[✓] Good

Rendering Pipeline

The JPQL query runs on the server before the page renders. Efficient queries reduce server processing and data transfer, speeding up the browser's rendering.

→Server Processing

→Network Transfer

→Browser Rendering

⚠️ BottleneckServer Processing and Network Transfer due to large or inefficient queries

Core Web Vital Affected

LCP

This affects database query execution time and how quickly data is fetched and rendered on the page.

Optimization Tips

1Always filter data in JPQL queries to reduce response size.

2Avoid fetching unnecessary fields or records in @Query.

3Use pagination with JPQL to limit data per request.

Performance Quiz - 3 Questions

How does using a filtered JPQL @Query affect page load performance?

A It increases data size and slows down loading.

B It reduces data size and speeds up loading.

C It has no effect on performance.

D It blocks rendering indefinitely.

DevTools: Network

How to check: Open DevTools, go to Network tab, filter by XHR or Fetch, and observe the size and timing of API responses.

What to look for: Look for smaller response sizes and faster response times indicating efficient queries.