Coding questions: String Compression problem, producer-consumer problem, readers-writers problem, check valid BST, improvise on the same problem with iterative tree traversal provided parent pointers in struct definition using O(1) extra space, implement strstr(), implement a simple regex matcher supporting '?' and '*' wildcards Other questions include OS and Networking basics, difference between TCP/UDP and when to use them, TCP flow and congestion control algorithm (how TCP reacts to a certain scenario), HTTP header contents, What is DNS and its response types, What happens when you enter a URL in web browser, mutexes and critical section, draw stack and contents of a given C program, how to efficiently serialize and deserialize a tree using a database table (basically asked me to draw the fields of the SQL table and describe the process)