Refactor blocking Python code to async without breaking it silently

Refactor the code below from synchronous to async — but only where it actually matters. Do not prefix every function with async def reflexively; that adds overhead without benefit for CPU-bound code and creates a false sense of concurrency.

CODE
def fetch_all_prices(product_ids: list[str]) -> list[Price]: loops and calls requests.get() per id

I/O OPERATIONS INVOLVED
HTTP GET requests to a pricing API, a write to a local CSV file

GOAL
fetch prices for up to 50 products concurrently instead of one request at a time

REQUIREMENTS
1. For each I/O operation, identify whether an async-native library exists (httpx's AsyncClient instead of requests, an async database driver instead of a sync one, aiofiles for file I/O) and use it. If no async equivalent exists for something in HTTP GET requests to a pricing API, a write to a local CSV file, say so explicitly and wrap it with asyncio.to_thread rather than calling it directly inside an async def and silently blocking the event loop.
2. Any genuinely CPU-bound work (parsing, computation) stays synchronous, or is offloaded to asyncio.to_thread or a ProcessPoolExecutor if it's heavy enough to matter — making it async def alone does nothing for CPU-bound code.
3. Use asyncio.gather, or a TaskGroup on Python 3.11+, to run independent I/O calls concurrently where fetch prices for up to 50 products concurrently instead of one request at a time calls for it — don't await a list of calls sequentially and call it async.
4. Propagate cancellation and timeouts correctly: wrap calls that should have a deadline in asyncio.timeout(...), and don't swallow asyncio.CancelledError with a bare except Exception.
5. Every function whose signature changes from sync to async must have every one of its callers updated too — list them, don't leave a caller doing result = my_func() on a coroutine it never awaits.

OUTPUT FORMAT
1. The refactored code.
2. A table: function name, sync or async now, and the reason.
3. Every caller found that also needed updating, and confirmation each one now awaits correctly.