The first coding question was about implementing validation for an on-call scheduling, and merging two on-call schedule lists, a list of standard schedule entries and a list of overrides. The second coding interview question was a different codebase. I needed to extend a code calculating the pay by hour for each on-call engineer, the extension needed to read new pay rates from config files for holidays like new year and Christmas. Watch out for someone being on-call across different hours with different pay rates. They will tell you that it is more important that you explain the solution and that you arrived to a shared understanding, this is not true. If you don't implement the solution, you will fail.