Kagi uses flow based programming to manage control flow
29 January 2025
Zac Nowicki from Kagi on how Flow Based Programming is used to manage control flow:
‘After launching Kagi, we realized we needed to manage a ton of concurrent tasks, combined with even more checks and decision making. We needed to stay on top of a robust concurrent control flow, and not go crazy trying to debug it all. This was the motivator for the "second generation" backend.
‘Flow Based Programming (FBP) is the hidden gem we followed to build observable and complex concurrent systems. FBP is a methodology introduced in around the 1970s, and we use a modern variant that takes the simple ingredients:
Simple "black box" interface. One message in → multiple messages out FIFO queues. First in, first out Routing table. This describes how messages are transferred between components ‘These three components produce a system so "regular" that you can describe control flow with any off-the-shelf diagramming tool. Put simply, we could create visualizations of our system representing the full source of truth; we just needed to write an interpreter for it!
Rather than creating UMl diagrams of software architecture that are then implemented in code the diagrams are the code. This means the visual representation of the system is always up to date.
It's always interesting to see what a small startup is doing when competing against a large incumbent.
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