The hiring process consisted of multiple stages:

• First, an automated coding skills quiz.
• Then, a one-way interview to assess communication skills.
• Next, a coding challenge in CodeSignal.
• Afterwards, a take-home exercise.
• This was followed by a series of interviews, including technical questions about the submitted exercise solution and open questions regarding system architecture design.
• The final step was an interview with the CTO of the company.

How would you design a scalable system for processing PDF files uploaded by users?