Example of a WriteConflict and concurrency lock based errors

writeConflict.js

async function updateUserAge(userName, session) { 
  // update the user 
}

// SENARIO - 1
// this will throw a WriteConflict error because of Concurrency Lock
await Promise.all([
  runInTransaction(async session => { await updateUserAge('John', session) }),
  runInTransaction(async session => { await updateUserAge('John', session) }),
]);

// SCENARIO - 2
// this is also likely cause an error as they might concurrently try to edit the same entry
// even though they are in the same session
await runInTransction(async session => {
  await Promise.all([
    updateUserAge('John', session),
    updateUserAge('John', session),
  ]);
});