Refresh token pattern in Spring Boot - Performance & Optimization

Performance: Refresh token pattern

MEDIUM IMPACT

This pattern affects the responsiveness and load on the backend server during user authentication refresh cycles.

Handling user session renewal without blocking user actions

Spring Boot

Use silent background refresh of access tokens before expiry with asynchronous calls, allowing user actions to continue.

Reduces blocking calls and spreads token refresh load, improving responsiveness.

📈 Performance GainImproves INP by reducing input wait times; user actions are not blocked.

Handling user session renewal without blocking user actions

Spring Boot

On every API request, the client sends the refresh token to get a new access token synchronously before proceeding.

This causes blocking network calls and delays user interactions, increasing input latency.

📉 Performance CostBlocks rendering and user interaction for 100-300ms per request during token refresh.

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Synchronous token refresh on every request	Minimal	0	0	[X] Bad
Asynchronous background token refresh	Minimal	0	0	[OK] Good
Storing refresh token in localStorage	N/A	N/A	N/A	[X] Bad
Storing refresh token in HttpOnly cookie	N/A	N/A	N/A	[OK] Good

Rendering Pipeline

Refresh token pattern mainly affects backend communication and user input responsiveness rather than direct rendering.

→Network

→JavaScript Execution

→Idle Time

⚠️ BottleneckBlocking synchronous token refresh calls increase input latency.

Core Web Vital Affected

INP

This pattern affects the responsiveness and load on the backend server during user authentication refresh cycles.

Optimization Tips

1Avoid synchronous token refresh calls that block user input.

2Use asynchronous background refresh to improve interaction speed.

3Store refresh tokens securely in HttpOnly cookies to reduce forced re-authentication.

Performance Quiz - 3 Questions

What is the main performance benefit of using asynchronous background refresh tokens?

A Blocks rendering until token refresh completes

B Increases server load by refreshing tokens more often

C Reduces blocking user input and improves interaction responsiveness

D Stores tokens in localStorage for faster access

DevTools: Performance

How to check: Record a session while triggering token refresh; look for blocking network calls and long scripting tasks.

What to look for: Long blocking times during token refresh indicate poor pattern; smooth interaction shows good pattern.