Web dev still has tons of weird bugs, tend to be in the interactions between multiple frameworks and edge cases in the assumptions they make. Like, I had one is

Web dev still has tons of weird bugs, tend to be in the interactions between multiple frameworks and edge cases in the assumptions they make. Like, I had one issue with intermittent test failures in Ruby on Rails, not reproducible with any fixed seed, and not affecting production. The overall source of it was: 1. We had a table from a third-party API that used their ID as a primary key, I believe stored as a string. 2. Ruby on Rails believed that it should make sure that primary keys aren't a too-large-to-store integer before attempting to save a row. 3. Our test suite would generate fake hexadecimal strings for the primary key for testing purposes for the table. 4. Sometimes, the hexadecimal string would have enough leading 0-9 digits that when Rails coerced it to an integer for their own internal checks, it would exceed the integer limit it thought the table ought to have. I honestly only figured it out by getting lucky.