They interview people from companies that are competitors of Radisys in the market, ask core architecture and design questions(which they should not ask a person from competitor company). Once they get all answers, they will not hire or give offer letter. HR will give some lame reason and reject the candidate. They don't have the intention to hire the candidate, pay them for the knowledge and experience they bring. In the name of interview, they want to extract knowledge from the candidate to know how other companies have implemented the core modules.

Technical : In-depth questions based on your resume, projects, and experience Core topics depending on your domain: For protocol stack/telecom: MAC, RLC, PDCP, 5G NR, timers, call flows, logs For software: Data structures, OS concepts, memory management, debugging OS/Linux: Threads, synchronization, IPC, system calls May include: Whiteboard/pseudo code Debugging a code snippet Explaining architecture or a design decision