Dejan Miličić, Head of R&D at RavDB and a seasoned software consultant with 25 years of experience, discusses the essence of maintaining software systems over time. He emphasizes that developers spend 90% of their time on change requests rather than building new systems. Dejan dives into CQRS, exploring its benefits in system design, while addressing common misconceptions. He also warns against premature optimization and vendor lock-in, advocating for a deep understanding of historical programming practices to enhance modern development.