The process took two months.

I applied online, then I had to pass a coding test with four questions in 90 minutes (they were really big questions, so be prepared).

After that, I had to pass a system design interview with the lead and senior developer of the team, who were really smart and good people.

Following this, I had an interview with the hiring manager, and finally, an interview with the director of software engineering working from California.

However, two to three weeks later, they changed their mind and wanted a senior developer, so they changed their offer and restarted the process. The HR told me I had only green flags, but their needs had changed.

What are the patterns in system design?