For clients not supporting HTTP/2, but the slower HTTP/1.1, request grouping is one of the 'best practises' to improve performance.
This is a demonstration on how to group requests, if you support this as a fallback.
Examples on
More on batch requests: https://www.developer.saxo/openapi/learn/batching-requests
Interactive demo: https://saxobank.github.io/openapi-samples-js/batch-request/