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Take-home coding exercise: ShiftAdd

When completing the exercise, please consider the following:

  1. Allow no more than 3 hours to complete the exercise. (Mostly because I find it useful to set a limit, otherwise the temptation to just make one more change can be endless!)
  2. It's fine to use any resources that you could use in your job; Google, Stack Overflow, etc. But the code you submit should be your own.
  3. We use Python a lot at Shift Lab, so solutions in Python are preferred.
  4. Please include documentation explaining how to run your code


ShiftAdd is a multiplayer online quiz game - think Wordle where there is a new challenge every so often but only one live challenge at any time.

Given the specification below, your task is to write a server implementation for ShiftAdd.


The server should randomly generate a new challenge every 30 seconds.

A challenge looks like this:

Challenge {
  int id;
  int a;
  int b;
where a and b are random numbers 0 <= a, b < 100

Only one challenge is live at any given time. The solution to a challenge is a + b.

The server is only required to persist state in memory.


A player of the game (i.e. a client of the server), can only submit one solution per challenge. A submission should be rejected if it is not for the current challenge.

For a submission for the current challenge, the server should return a score to the player. The score is calculated as how much time is left in the lifetime of the current challenge (to hundredths of a second), i.e. quicker answers get a higher score! An incorrect solution receives a score of -1.


Upon request:

  • The server should return a player's mean score, number of challenges taken part in, and longest streak of correct solutions without missing a challenge.
  • The server should return the mean score for a given challenge (for all players that took part).

Good luck!

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