From 1e5ea74c57fea00ee42bbc3eda768a8ae0948c32 Mon Sep 17 00:00:00 2001
From: Dalton <daltojohnso@users.noreply.github.com>
Date: Thu, 6 Jan 2022 11:00:33 -0800
Subject: [PATCH] add mention of FS_CACHE to devenv.md (#19541)

---
 docs/developers-guide/devenv.md | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/docs/developers-guide/devenv.md b/docs/developers-guide/devenv.md
index 894949b6313..97094885d13 100644
--- a/docs/developers-guide/devenv.md
+++ b/docs/developers-guide/devenv.md
@@ -62,6 +62,14 @@ $ yarn build-watch
 
 Some systems may have trouble detecting changes to frontend files. You can enable filesystem polling by uncommenting the `watchOptions` clause in `webpack.config.js`. If you do this it may be worth making git ignore changes to webpack config, using `git update-index --assume-unchanged webpack.config.js`
 
+By default, these build processes rely on a memory cache. The build process uses a large amount of memory and may take a considerable amount of time to start (1 - 2 minutes or more). FE developers (or anyone else who frequently restarts FE builds) are encouraged to use webpack's filesystem cache option for much better start-up performance:
+
+```sh
+$ FS_CACHE=true yarn build-hot
+```
+
+When using `FS_CACHE=true` you may need to remove the `node_modules/.cache` directory to fix scenarios where the build may be improperly cached, and you must run `rm -rf node_modules/.cache` in order for the build to work correctly when alternating between open source and enterprise builds of the codebase.
+
 ## Frontend testing
 
 Run all unit and Cypress end-to-end tests with
@@ -72,6 +80,8 @@ yarn test
 
 Cypress tests and some unit tests are located in `frontend/test` directory. New unit test files are added next to the files they test.
 
+If you are using `FS_CACHE=true`, you can also use `FS_CACHE=true` with `yarn test`.
+
 ## Frontend debugging
 
 By default, we use a simple source mapping option that is optimized for speed.
-- 
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