Async for slow work

When code performs potentially slow CPU/crypto work, avoid blocking the event loop. Prefer a Promise/callback-based asynchronous wrapper so the runtime can continue handling other work, and keep the function’s API surface consistent so it can replace a sync version without call-site changes. Also ensure your team’s documentation defines async accurately (e.g., “allow multiple events to trigger code without waiting for each other”).

Example (async wrapper that preserves the same call pattern):

const crypto = require('crypto');

const hashNode = (val) =>
  new Promise((resolve) => {
    // Yield so other events can run before doing the expensive work
    setImmediate(() => {
      resolve(crypto.createHash('sha256').update(val).digest('hex'));
    });
  });

Apply this especially to server/request-heavy code paths where long hashing can delay other requests.