Replay is developing a time-travel debugger for JavaScript, specifically targeting the challenge of intermittent browser test failures by working on a side project called Replay Visuals. This project, hosted on Vercel and backed by Supabase, aims to save snapshots from browser test runs and streamline the workflow for approving visual regressions. A significant challenge encountered was managing GitHub Check Runs, as they can only be handled via GitHub Apps rather than personal tokens. This necessitated the creation of a GitHub App to generate a JSON Web Token (JWT) and subsequently a token for the Check Run. The process involved overcoming hurdles with JWT creation, such as ensuring correct time calculations and avoiding expiration-related errors by setting an expiration 9 minutes in the future. Despite the availability of GitHub's Octokit library for authentication, the developers found it more effective to break the problem into smaller parts rather than relying on the library, suggesting that Octokit could enhance its setup process with better error messages and troubleshooting documentation.