The basic difference between the two frameworks is that nanoservices are considered smaller siblings of microservices. Nanoservices are designed to perform a single function, whose output is exposed through a specific API endpoint (command).

Nanoservices are fully discoverable among each other. Each one can link with other services to perform additional actions and extend functionality.

By design, nanoservices are:

Self-contained

Reusable

Less complex than microservices

Supported by distinct function files for each

Nanoservices are considered more efficient than microservices, particularly due to:

Ease of initial setup

Reduced latency among services, where each nanoservices’ function code can be executed on-demand without the use of dedicated containers or servers to host every individual service.

https://www.bmc.com/blogs/microservice-vs-nanoservice/