javascriptAsync race conditionHard

High-traffic vote counters returning low totals

Time: 0:00

What it should do

tallyVotes(votes) should add up every vote, so tallyVotes([1, 2, 3, 4]) returns 10.

What goes wrong

tallyVotes([1, 2, 3, 4]) returns 4 instead of 10. Only the last vote seems to survive.

Hints

This is an async and race conditions bug

A missing await, results in the wrong order, and updates that overwrite each other under load.