Native SQL queries in Spring Boot - Performance & Optimization

Performance: Native SQL queries

MEDIUM IMPACT

Native SQL queries impact server response time and data fetching speed, which affects how fast the page can start rendering.

Fetching data from the database for a web page

Spring Boot

String sql = "SELECT id, name, email FROM users WHERE active = true LIMIT 100";
List<User> users = entityManager.createNativeQuery(sql, User.class).getResultList();

Limits data to needed columns and rows, reducing data size and query time.

📈 Performance GainReduces server response time by 50% or more, improving LCP

Fetching data from the database for a web page

Spring Boot

String sql = "SELECT * FROM users";
List<User> users = entityManager.createNativeQuery(sql, User.class).getResultList();

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

📉 Performance CostBlocks server response for longer, increasing LCP by hundreds of milliseconds on large tables

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Fetching all data without filters	N/A (server-side)	N/A	Delays initial paint	[X] Bad
Fetching filtered, limited data	N/A (server-side)	N/A	Speeds up initial paint	[OK] Good

Rendering Pipeline

Native SQL queries run on the server before the browser rendering starts. Faster queries mean faster data delivery, enabling quicker HTML generation and browser painting.

→Server Data Fetching

→HTML Generation

→Browser Rendering

⚠️ BottleneckServer Data Fetching

Core Web Vital Affected

LCP

Native SQL queries impact server response time and data fetching speed, which affects how fast the page can start rendering.

Optimization Tips

1Always filter and limit data in native SQL queries to reduce server response time.

2Avoid selecting unnecessary columns or rows to minimize data transfer.

3Use database indexes to speed up query execution and reduce delays.

Performance Quiz - 3 Questions

How does limiting columns and rows in a native SQL query affect page load?

A It causes more reflows in the browser.

B It increases the number of DOM nodes.

C It reduces server response time, improving LCP.

D It has no effect on performance.

DevTools: Network

How to check: Open DevTools, go to Network tab, reload page, and inspect the API or page request timing.

What to look for: Look at the Time to First Byte (TTFB) and total response time to see if server queries delay loading.