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Maxim Sakhno @maxim-sakhno.bsky.social · 28/01/2026

But wait... didn't LiteStar beat FastAPI in their own benchmarks? Ah, they used nested dependencies only! That explains it. 💡

A technical benchmark report titled "Dependency injection" comparing FastAPI 0.101.1, LiteStar 2.0.0, and Sanic 23.6.0. The top section lists test cases for resolving 3 nested dependencies in synchronous, asynchronous, and mixed modes. Below, a complex bar chart shows "Requests per second (higher is better)" across these modes. LiteStar significantly outperforms the others in almost every category, particularly in asynchronous dependency resolution, which sets the stage for the specific performance "cliff" discovery detailed in the rest of the thread.

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Maxim Sakhno @maxim-sakhno.bsky.social · 28/01/2026

So, what kind of dependency graph are they actually testing? 🧐 Let’s dig into the official benchmark source code. Link: docs.litestar.dev/latest/bench... Take a look at the setup below. What do you see? 👇

A screenshot showing Python code and a flow diagram explaining asynchronous dependency injection. The code defines three asynchronous functions—async_dependency_one, two, and three—where each subsequent dependency injects the previous one. An API route handler async_dependencies_async then injects all three. Below the code, a diagram shows a "handler" box pointing down to "dep 1", "dep 2", and "dep 3", with horizontal arrows indicating that "dep 3" depends on "dep 2", which in turn depends on "dep 1".

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Maxim Sakhno @maxim-sakhno.bsky.social · 28/01/2026

Mystery solved! 🔍 In the official benchmark, the graph is just a linear chain. It results in stages with exactly one dependency each. Since there’s nothing to parallelize, TaskGroups aren't even triggered! Look at this linear "batching" below. 👇

A technical diagram showing the batching logic for a sequential dependency chain. On the left, a "Dependency Graph" shows a strict vertical hierarchy where Dep3 depends on Dep2, and Dep2 depends on Dep1. An arrow labeled "Kahn's Algorithm" points to the right, showing these nodes split into three individual batches: Batch 1 (Dep1), Batch 2 (Dep2), and Batch 3 (Dep3). Each batch contains only one node and is labeled "Await," indicating that the system will resolve them sequentially rather than using parallel TaskGroups.

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