Quite often, applications that you might believe would exceed the Xero API rate limits, can in fact work within the limits by analysing the structure of how you intend to use the Xero API
You can do more than one thing in a single request: For example, you can create more than one Invoice in a single PUT or POST Invoices API call. While there is no upper limit in the number of nodes that can be sent at one time, a ceiling of about 50 nodes per request is practical - this will ensure a request does not exceed the maximum size of 3.5MB. You should also review our notes on summarizing validation errors.
If you are hitting rate limits because you retrieve a large amount of data from Xero there are a couple of features you should be taking advantage of:
You can use pagination to retrieve line item details for 100 items (e.g. Invoices) at a time. Endpoints on the Accounting API that currently support pagination are invoices, contacts, bank transactions and manual journals. All major endpoints on the Payroll, Files and Assets APIs also support paging.
Use the If-Modified-Since header to retrieve only what's changed since your previous request