There are typically two stages of technical interview and one stage of HR grooming. The last stage is basically held for salary negotiation. The first stage is to check the candidate's basic knowledge and skill set as a backend software engineer. To be specific, the questions are entirely on DSA, OOP, the application framework he has worked on throughout his professional journey, and basic RDBMS. The second stage is packed with a bit more advanced topics. Some of the questions may arise from your professional experience. Some questions may be presented to you as some probable real-life scenarios, and how you would tackle those. If you are a backend engineer, you may be asked about the necessity of API gateways, design principles, and how you have applied them, some complex SQL problems, load balancer, and the list goes on. Please note that you should present a certain skill before the interviewer only if you are sure that you have in-depth knowledge of that. This should be done in your resume too.