Yet another presentation about Event Sourcing? Yes and no. Event Sourcing is a really great concept. Some could say it’s a Holy Grail of the software architecture. True, but everything comes with a price. This session is a summary of my experience with ES gathered while working on 3 different commercial products. Instead of theoretical aspects, I will focus on possible challenges with ES implementation. What could explode? How and where to store events effectively? What are possible schema evolution solutions? How to achieve the highest level of scalability and live with eventual consistency?