# Post metadata

## Title

Why Your Spring Boot App Takes 8 Seconds to Start: A Bean-by-Bean Diagnosis

## Slug

`spring-boot-startup-time-bean-by-bean-diagnosis`

## Excerpt

Spring Boot logs one startup number and hides four phases behind it. This walks through
turning on the `ApplicationStartup` instrumentation that ships switched off, reading the step
tree by self time rather than total duration — the mistake that makes people optimise a bean
costing 10 ms instead of the one costing 504 — and then puts measured numbers on component
scanning (0.11 ms per class inspected, whether or not it is a bean), on the silent truncation
a 2048-step buffer performs on your recording, and on the JDK 25 AOT cache, which took
6.93 s to 4.82 s on the companion project without a line of application code changing.

## Categories

| Category | Term ID |
|---|---|
| Java | 328 |
| Spring | 355 |

## Yoast

| Field | Value |
|---|---|
| `_yoast_wpseo_title` | Spring Boot Startup Time: A Bean-by-Bean Diagnosis |
| `_yoast_wpseo_metadesc` | Turn on Spring Boot's built-in startup instrumentation, read the step tree by self time, and see measured numbers for component scanning, buffer truncation and the JDK 25 AOT cache. |
| `_yoast_wpseo_focuskw` | spring boot startup time |

## Files

| File | Contents |
|---|---|
| [`post.md`](post.md) | article body, Markdown |
| [`images/01-self-time-vs-total-time.svg`](images/01-self-time-vs-total-time.svg) | the same 400 steps ranked by total duration and by self time |
| [`images/02-buffer-truncation.svg`](images/02-buffer-truncation.svg) | what a 2048-step buffer keeps and what it silently drops |

## Companion project

[`spring-boot-startup-time/`](..) in `asmhatre/spring-boot-demo`.

## Jira

[BLOG-618](https://ankurm.atlassian.net/browse/BLOG-618)

## Verified against

Spring Boot 4.1.1 (GA 20 August 2026), Spring Framework 7.0.9, Spring Data JPA 4.1.1,
Hibernate ORM 7.4.5.Final, Tomcat 11.0.24, Micrometer 1.17.1, H2 2.4.240,
Temurin 25.0.4.1+1 LTS, Maven 3.9.11 — see
[`docs/output/00-versions.txt`](../docs/output/00-versions.txt).