How would you implement a FastAPI endpoint that accepts query parameters for department, min_salary, and sort_by, validates them with Pydantic, and returns a filtered and sorted list of employees?

Define a Pydantic model for the query: class EmployeeFilter(BaseModel): department: str | None = None; min_salary: int = 0; sort_by: Literal['id','department','salary'] = 'id'. In FastAPI, create an endpoint: @app.get("/employees") async def get_employees(filter: EmployeeFilter = Depends()): Inside, filter the in‑memory list: filtered = [e for e in employees if (filter.department is None or e['department'] == filter.department) and e['salary'] >= filter.min_salary]. Sort: sorted_emps = sorted(filtered, key=lambda e: e[filter.sort_by]). Return sorted_emps. FastAPI automatically parses query parameters into the Pydantic model, validates types, and returns 422 on invalid input. Complexity remains O(n log n) for sorting. This pattern keeps validation logic separate, makes the endpoint clean, and leverages FastAPI’s dependency injection.