Event-based applications are by no means new kids on the block, yet a lot can be told about how to use Azure to unleash their power without having costs soaring. The ingredients list is quite simple: a CosmosDB-backed event store, SQL Azure for read model(s) and some computing options to run back-end services. Picking up technologies in a cost savvy way, though, isn’t trivial due to the amount of viable options: should you go PaaS or IaaS? Where do containers fit in this context? Is serverless a viable option? Let me show you what I’ve learned and the mistakes I made throughout a 5-years long journey.