Consistent Shard

q4.rb

# Append shard ranges as new shard groups are brought online                     
# Format: [Cutoff User ID, Min Shard, Max Shard]                                 
USER_ID_SHARD_MAPPING = [                                                        
    [0, 1, 10],                                                                  
    [30000, 11, 20],                                                             
    [500000, 21, 50],                                                            
]                                                                                
                                                                                 
# Consistent shard that falls within a shard range by the user’s ID 
def consistent_shard(user)                                                       
    *, min, max = USER_ID_SHARD_MAPPING.                                         
        select { |s| s[0] < user.id }.last                                       
                                                                                 
    (user.id % max - min) + min                                                  
end