Visualizing AWS Lambda Durable Function Workflows with durable-viz

If you're new to durable functions, start with the durable functions post for the core concepts. The short version: your handler re-runs from the beginning on every resume, but completed steps return cached results instantly instead of re-executing. The SDK handles this checkpointing and replay transparently. Durable functions encourage you to write sequential code. But the execution flow isn't always sequential. You have parallel branches that fan out and converge. Conditionals that route to callbacks or skip to the end. Invocations that call other Lambda functions. The more primitives you use, the harder it gets to see the full picture just by reading the handler. I hit this when building the purchasing coordinator. Five specialist agents dispatched in parallel, a conditional approval callback, plan and synthesis steps on either side. The code reads top to bottom, but the workflow branches and converges in ways that aren't obvious from the source. Two primitives in particular: contex