Isolates (Cloudflare Workers)
Nanoservices are a new model that achieve the benefits of independent deployment with overhead closer to that of library calls. With workerd, many Workers can be configured to run in the same process.
Each Worker runs in a separate "isolate", which gives the appearance of running independently of the others: each isolate loads separate code and has its own global scope.
However, when one Worker explicitly sends a request to another Worker, the destination Worker actually runs in the same thread with zero latency. So, it performs more like a function call.
A second big architectural difference between workerd and other runtimes is how it handles built-in APIs.
Many runtimes implement significant portions of their built-in APIs in JavaScript, which must then be loaded separately into each isolate.
workerd does not; all the APIs are implemented in native code, so that all isolates may share the same copy of that code. These design choices would be difficult to retrofit into another runtime, and indeed these needs are exactly why we chose to build a custom runtime for Workers from the start.