Is there any chance to use thread pool?

If we can only use one work-thread, async/await may not be so useful. Using one work-thread for each individual work root might be wasting.Using multiple threads is not an urgent though. WASM is an option.

The issue names no files, tests, or entry points. Start by tracing how work threads and individual work roots are currently handled, then investigate whether a thread pool or WASM approach fits the existing design. Done would require a decided, implemented approach for using multiple threads, with its behavior verified.

Written by the indexing model from the issue text.