Which HTTP method should be used to implement a method for retrieving 100+ thousand employees with filtering?

To obtain a large volume of data with filtering (100+ thousand employees), the HTTP GET method is usually used, as it is intended for retrieving resources. However, considering the volume of data and the complexity of filtering, it is important to consider URL limitations (request string length) and performance.

If the filters are complex and passing them in the URL is inconvenient, the POST method can be used with the request body, where filtering and pagination parameters are passed. This is a common practice for complex queries, although formally POST is intended for creating resources.

Summary:

• If filters are simple and fit within the URL — use GET with parameters and pagination.
• If filters are complex and data volume is large — use POST with the request body, implement pagination and lazy loading (e.g., cursors or offset/limit).

Example of a POST request for filtering:

POST /api/employees/filter
{
  "department": "sales",
  "ageRange": {"min": 25, "max": 40},
  "page": 1,
  "pageSize": 1000
}