Clean Async TypeScript

Async code should make ordering, ownership, and failure behavior explicit. Race-prone behavior deserves small units and direct tests.

A1: Isolate Async Workflows

Keep orchestration separate from pure transformation. Parse, validate, map, and calculate in synchronous helpers when possible; let async functions coordinate I/O.

async function importUsers(file: FileHandle, repository: UserRepository) {
  const rows = await file.readRows();
  const users = rows.map(parseUserRow);
  await repository.saveMany(users);
}

A2: Make Ordering Explicit

Use sequential await when order matters and Promise.all when operations are independent. Do not rely on array callbacks with hidden promise behavior.