Driven by consumer expectations and the proliferation of IoT, by 2023 30 percent of all the world’s data will be consumed in real time – that’s 1.5 times the entire amount of data consumed today. Corresponding to this, by 2020, 50 percent of APIs will be event-driven. In this talk, I explore the often unforeseen complexities involved in both publishing and consuming event-driven APIs as adoption increases. Whilst initiatives like AsyncAPI are making significant progress in helping to define machine and human readable specifications, developers still need to think hard about which dimensions they want their event-driven APIs to deliver on in the future, before they dive in. I will take you on a tour of different protocols that each address event-driven API challenges with varying proficiency, diving into five key complexities: integrity vs. latency, throughput, push and pull subscriptions, downstream reliability and durability. At the end of this talk I hope you will see that there is no silver bullet, but there are insights you can take from real-world problems we’ve seen first-hand, and apply that to the event-driven realtime APIs you are publishing or plan to publish soon.