Incremental builds with data in Astro - Step-by-Step Execution

Concept Flow - Incremental builds with data

Start Build

↓

Check Data Changes?

No→Skip Build for Unchanged Pages

Yes↓

Fetch Updated Data

↓

Generate Only Changed Pages

↓

Update Build Cache

↓

Finish Build

The build process checks if data changed, then only rebuilds pages with updated data, skipping unchanged ones to save time.

Execution Sample

Astro

const pages = ['home', 'about', 'blog'];
const changedPages = ['blog'];
for (const page of pages) {
  if (changedPages.includes(page)) {
    buildPage(page);
  }
}

This code rebuilds only pages that have changed data, skipping others.

Execution Table

Step	Page	Data Changed?	Action	Output
1	home	No	Skip build	No output
2	about	No	Skip build	No output
3	blog	Yes	Build page	blog page rebuilt
4	End	-	-	Build complete, only blog rebuilt

💡 All pages checked; only 'blog' had data changes, so only it was rebuilt.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
page	-	home	about	blog	-
changedPages	['blog']	['blog']	['blog']	['blog']	['blog']
buildStatus	{}	{home: 'skipped'}	{home: 'skipped', about: 'skipped'}	{home: 'skipped', about: 'skipped', blog: 'built'}	{home: 'skipped', about: 'skipped', blog: 'built'}

Key Moments - 2 Insights

Why does the build skip some pages even though they exist in the pages list?

Because the build checks if the page's data changed (see execution_table steps 1 and 2). If not changed, it skips rebuilding to save time.

How does the build know which pages to rebuild?

It uses a list of changedPages (see variable_tracker 'changedPages') and rebuilds only those pages included in that list.

Visual Quiz - 3 Questions

Look at the execution table, what action is taken for the 'about' page at step 2?

A Skip build

B Build page

C Fetch data

D Update cache

💡 Hint

Check the 'Action' column for step 2 in the execution_table.

At which step does the build process rebuild a page?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for 'Build page' in the 'Action' column in execution_table.

If 'about' page data changed too, how would the buildStatus change after step 2?

A {home: built, about: built}

B {home: skipped, about: built}

C {home: skipped, about: skipped}

D {home: skipped, about: built, blog: built}

💡 Hint

Refer to variable_tracker and imagine 'about' added to changedPages list.

Concept Snapshot

Incremental builds check which pages have updated data.
Only those pages are rebuilt.
Others are skipped to save time.
This speeds up the build process.
Use a list of changed pages to control rebuilds.

Full Transcript

Incremental builds with data means the build system looks at which pages have new or changed data. It then rebuilds only those pages, skipping the rest. This saves time and resources. In the example, three pages exist: home, about, and blog. Only the blog page has changed data, so only it is rebuilt. The buildStatus variable tracks which pages were built or skipped. This approach makes building faster by avoiding unnecessary work.