On Mastra Cloud, It took a long time (~13 seconds) to return a 404 when I was trying to get a run using a "runId" that doesn't exists. I have a use case for "non-existing runId" so I need to call the API this way. It was returned instantly if the "runId" exists.
My own deployment doesn't have this problem. It could be that my deployment was using a lower version of Mastra Core, but I haven't tried the latest versions to rule this out.