The text recounts the challenges faced by a service called brand.dev, which experienced severe performance issues due to catastrophic backtracking in a regular expression (regex) used for parsing HTML. Initially, the team suspected scaling problems, but after extensive investigation, they discovered that a single regex pattern was causing CPU overload due to millions of backtracking operations triggered by malformed HTML. This phenomenon, known as Regular Expression Denial of Service (ReDoS), was resolved by replacing the problematic regex with Google's RE2 engine, which avoids exponential backtracking. Ultimately, the team transitioned to using Cheerio for HTML parsing, which significantly improved performance and reliability. The company learned valuable lessons about the importance of using proper HTML parsing tools and implementing safeguards like timeouts to prevent similar issues in the future. This experience underscored the broader industry challenge of handling HTML parsing reliably and securely.