Issue
Installing node_modules with npm versions 6.14.15, 6.14.16, 6.14.17, etc. takes an extremely long amount of time, something like 10x the normal build time.
npm version 6.14.15 introduced a security fix which happens to have a major impact on performance. The issue is outlined here: https://github.com/npm/cli/issues/3939#issuecomment-956958065.
Resolution
Pin npm to a recent, supported, and performant release. npm 8.x is suggested, as it's the actively maintained release. npm 6.14.13 is also known to fix the performance issue. However, it includes known security issues and is on the unsupported 6.x release line. To specify npm 8.x, modify package.json with:
"engines": {
"npm": "8.x"
}
If using Node.js 14.x, npm 6.x is the default npm shipped with Node.js. Node.js 16.x ships with npm 8.x by default. Upgrading to Node.js 16 will fix this issue (if npm version is not specified). To specify Node.js 16.x, modify package.json with:
"engines": {
"node": "16.x"
}