When the code scales so poorly in the face of large inputs that it cannot complete in a reasonable amount of time, use this instead of the [performance] tag.
Time-limit-exceeded issues (often abbreviated to TLE) are a special kind of performance problem, where the code handles small test cases very well, but takes an unreasonable amount of time to complete for larger inputs. You may use this tag instead of performance when an online judge rejects your solution to a programming-challenge due to time constraints, or when you need to interrupt your computation because it appears to take much too long to finish.
Questions should state an approximate time target.
Generally, these kinds of performance issues cannot be resolved by making local optimizations, but require a smarter algorithm with better complexity characteristics.
