A short but thorough discussion about my current role and the AP role in MOT - basically a trading platform and OMS in C#. The rest is a 90 minutes purely technical discussion from messaging middleware to buffer size, message throughput, processing latency, threading design, TCP/UDP, message loss, retransmission, async call, callback and delegates, etc. Given a certain scenario, with the use of sequence diagrams, required to draw messages flows and where exactly should threads got branched, such that end user UI wouldn't be blocked. After these, there are several extremely common but basic questions: polymorphism and OOP, boxing and unboxing and heap/stack, plus database design - normalization, table join, index/key, subqueries. Given this is an experienced hire instead of graduate recruitment, question set is relatively easy.