At the beginning, our system relied heavily on webhooks for communication between services. They were simple to implement and worked well for basic event delivery. However, as the system evolved into a multi-agent environment with higher reliability requirements, the limitations of webhooks became increasingly apparent.
The first problem was reliability. Webhooks are inherently transient: if a receiving service is temporarily unavailable, events are often lost or require complex retry logic that is difficult to make robust. As the number of services increased, these edge cases became more frequent and harder to manage.
The second issue was ordering and consistency. In a distributed system where multiple events are generated rapidly, ensuring correct sequencing becomes critical. Webhooks provide no strong guarantees about ordering, which led to subtle state inconsistencies across components.
We also ran into observability challenges. Once an event was sent, it effectively disappeared into another system with limited visibility into its lifecycle. Debugging failures required stitching together logs from multiple services without a unified source of truth.
To address these issues, we moved to a persistent event bus architecture.
In this model, all events are written to a durable, centralized log before being consumed. Instead of pushing events directly to services, components subscribe to the event stream and process messages at their own pace. This creates a decoupled system where producers and consumers are independent in both timing and execution.
The persistent event bus introduces several important properties. First, durability: events are stored reliably and can be replayed if needed. Second, ordering guarantees within defined partitions ensure consistent state transitions. Third, replayability allows us to reconstruct system behavior for debugging, recovery, or backfills.
This shift also improved system scalability. New services can be added simply by subscribing to the event stream, without modifying existing producers. Similarly, failures in downstream systems no longer affect event generation.
Perhaps most importantly, the event bus became a foundation for system-wide observability. Instead of fragmented logs, we now have a unified timeline of all system activity, which makes reasoning about complex agent behavior significantly easier.
In retrospect, the move away from webhooks was not about replacing a tool, but about evolving from point-to-point communication to a shared system of record for all events.
