Slow Build Time Native Federation.

[fabianvieri]

For which library do you need help?

native-federation

Question

I got issue with native federation build time, when serving in development. I understand that the first build is slow and still caching. But for any subsequent build, its still slow when building the federation artifacts meanwhile the angular application builds is getting faster.

Right now, after cleaning .angular and native federation cache folder, also using option "cacheExternalArtifacts": true the build time is around 15-20s which is still significantly slower than the the application build. For context my setup is polyrepo and I have 6 exposed modules in this current projects.

Application bundle generation complete. [1.617 seconds] - 2026-02-13T07:48:55.350Z
INFO Building federation artefacts
DBG! 00:12:514.055ms - [build artifacts] - To bundle all mappings and exposed.

This issue is related to #559

logs.txt

Native Federation: 21.0.3
Angular: 21.0.5
Angular CLI: 21.0.3
Node: 24.12.0
NPM: 11.6.2
Browser: Chrome
Operation System: Windows 11

[Aukevanoost]

Thanks for this, I did a little bit of digging and unfortunately there is no easy answer.

So the part that's taking ~12s is the bundling of the exposed modules (not the externals). This happens as step 2 of the 3 steps (where step 3 is building the shell or main.ts as a regular Angular app). You can see it here: https://github.com/angular-architects/module-federation-plugin/blob/78dac9d0e0379f981893272315e14227ed12a896/libs/native-federation-core/src/lib/core/bundle-exposed-and-mappings.ts#L53C1-L65C8

And it's part of the building process:
https://github.com/angular-architects/module-federation-plugin/blob/78dac9d0e0379f981893272315e14227ed12a896/libs/native-federation-core/src/lib/core/build-for-federation.ts#L47C1-L52C7

Since all externals are built as one big bundle. I can't do much optimization there. The reason I asked if you had shared libraries was because they are also included in this bundle step.

Not all is lost though, Angular keeps track of which files have changed (you can see this in the logs). If we manage to tap into that info and break the bundling up into a bundle per exposed or smth, we can trigger a smaller bundle of only the files that changed. Do note that this is damage control and that it'll never be as fast as Angular SPA builds.

[fabianvieri]

Hi @Aukevanoost , thanks for the reply, so basically right now, it will build all exposed modules all over again even just one of the modules change?

[ladler1]

@Aukevanoost I understand that this is a complex task. What surprised me is that the build times for the federation artifacts are much worse compared to module federation. I do not have exact numbers but it is striking.

[fabianvieri]

Also I have done experimenting a bit, what I tried:

• clear .angular and cache folder
• exposed no modules
• share only core angular packages instead of using shareAll
• create minimal changes in one of the angular templates

After all above the federation still got around ~12s everytime when bulding artefacts on file change, so what actually affecting the build time?

[Aukevanoost]

@fabianvieri Interesting! I did some more digging and you're right! In my tests, 90% of the time it took to bundle the shared components was indeed used up by the angularCompiler.
here: https://github.com/angular-architects/module-federation-plugin/blob/78dac9d0e0379f981893272315e14227ed12a896/libs/native-federation/src/utils/angular-esbuild-adapter.ts#L281C1-L284C5

Perhaps it can be used more efficiently.