Behavior of Synchronous IO in ASP.NET Core Under Concurrent Load

Goal

Determine how enabling synchronous IO in ASP.NET Core affects request latency when the server handles many concurrent connections.

Constraints

The framework disables synchronous IO by default to prevent thread‑pool starvation. Legacy code may require it, but the documentation does not mandate a single configuration path.

Uncertainty

It is unclear whether the default setting is optimal for all workloads, and what thresholds of concurrency trigger noticeable latency spikes.

Questions

• What is the documented default policy for synchronous IO in ASP.NET Core 7.0?
• Under what concurrency levels does enabling synchronous IO lead to measurable thread‑pool starvation and latency degradation?
• Does the framework provide guidance on balancing legacy synchronous code with performance‑critical workloads?