the Suave extension for ASP.NET Core (https://www.nuget.org/packages/Suave.AspNetCore/) is fast and you can use lots of suave specific features, with same performant kestrel as base, because suave is added as middleware.

Or there is also a new attempt (https://github.com/dustinmoris/AspNetCore.Lambda) to use api similar to suave, more integrated with asp.net core itself (security/auth/etc).