Accidentally Quadratic: Evaluating trillions of event matches in real-time

Inngest is an event-driven system that allows developers to build functions capable of filtering over millions of events. It offers the flexibility of filtering and matching event-driven systems like Kafka without the need for managing or optimizing the system itself. The challenge lies in creating ephemeral event matchers that can be quickly added, evaluated, and removed due to their short-lived nature. Inngest's solution involves normalizing expressions and parsing them into abstract syntax trees (ASTs), then using in-memory indexes like hashmaps and B-trees for string equality matching within expressions. This allows the system to evaluate billions of expressions in real-time, reducing latency and improving performance.