[irq]: techie interrupted

The same instance type shows a different behavior depending on the region that it is running, this is particularly critical if you depend on multiple regions for disaster recovery or geographical load balancing

Generally speaking performance is better and more consistent in the South America region when compared to Virginia, this is probably due to the fact that SA region was the latest to be deployed. Maybe the SA datacenter uses new server models or it is just underutilized, but this is a wild guess

Write performance for the medium instance type in Virginia abruptly decays, dropping from almost 400 call/s to something around 300 calls/s, this is not very clear in the scatter plot but if you draw a time-based chart you can clearly see this pattern. This is the main reason you see two spikes in the density chart. Read performance in the SA small instance show a similar behavior.