Around a release, an indie developer or publisher needs to keep checking where their app ranks for several keywords on the App Store and Google Play and how that changes, in order to judge whether title, subtitle or keyword edits worked.
Searching the app stores by hand, or subscribing to a commercial ASO rank tracker.
Checking rankings by hand across countries and keywords in the app stores is slow and hard to turn into a continuous record; commercial ASO tools charge monthly subscriptions that are costly for solo developers.