Exam AWS Certified Database - Specialty topic 1 question 37 discussion

I'm going with D based on the following links. https://aws.amazon.com/blogs/database/amazon-dynamodb-gaming-use-cases-and-design-patterns/ "EA uses the user ID as the partition key and primary key (a 1:1 modeling pattern)." https://aws.amazon.com/blogs/database/choosing-the-right-dynamodb-partition-key/ "Partition key and sort key: Referred to as a composite primary key, this type of key is composed of two attributes. The first attribute is the partition key, and the second attribute is the sort key."

D is the best choice of keys for below requirements. ✑ Update scores in real time whenever a player is playing the game. -- user_id being partition key ✑ Retrieve a player's score details for a specific game session. -- game_id sort key

I go for D - user_ID for global score - user_ID (PK) + game_id (SK) for a session

- game_id must reflect the game session and not the actual game, because if not even user_id + game_id would not be unique. Saying that, game_id will have higher cardinality. - about the query... if it is to get the details of one specific player, both c and d will work, if we want to get the details of all players for a game, only c works. Having this said, for me C) is the only answer that will work for all cases, having a higher cardinality value as partition key. But let me say that these types of questions must be better elaborated, because at some times it dependends on the interpretation

this is my humble contribution to the solution: If we want to get the high score for a player for a certain game, user_id should be our partition key and game_id should be our sort key, which is D, but to find out what the highest score ever was for a certain game, we would need game_id to be a partition key and 'score' to be the sort key, which is not in the options. I mean that cardinality can be decided according to the objective of the query but it is not given explicitly in the question.

D. Game_id would have lower cardinality than user_id. Say the gaming company only had 4 games with 2m users. You would want your partition to be by higher cardinality and your secondary with lower.

I'm going with C, for queries and updates game_id and user_id are always used, in addition, game_id has more high cardinality and avoids "hot" partitions if used as the partition key.

D. There are going to be more user_ids than game_ids, hence user_id will be the higher cardinality value = the better partition key. For those of you saying "C", are you telling me Electronic Arts has more unique games than they have users!!??! https://aws.amazon.com/blogs/database/choosing-the-right-dynamodb-partition-key/

If there will be player_id it will cause of hot partitioning. So D is wrong. C is correct as game_id will have more high cardinality

C is the answer. ✑ Scores should be updated in real time anytime a player is engaged in the game. -> game_id is the partition key ✑ Retrieve the information of a player's score for a certain gaming session. - > game_id and user_id is the primary key (i.e. user_id is the sort key)

use cases: ✑ Scores should be updated in real time anytime a player is engaged in the game. (query based on user_id only => user_id partition key) ✑ Retrieve the information of a player's score for a certain gaming session.(query based on user_id + game_id=> user_id partition key, and game_id sort key) D. Create a composite primary key with user_id as the partition key and game_id as the sort key

Answer is C, partition key must have high cardinality ie. game_id as there may be multiple instances of games played by each user.

I chose D. GSI does not support strong consistency.

For me, both C and D can be used but C is better. ✑ Update scores in real time whenever a player is playing the game. => Query by the game_id first, then update relevant user_id with his relevant score. ✑ Retrieve a playerג€™s score details for a specific game session => game_id can be used to query then specify the user_id D can do the same as above. But for the query such as: Top score player for each game, C is better. D is for the query such as: This player plays how many games and the score of each.

Why not C ? Any idea ?

I would go with A. Reason, Need user_id as partition key for main table and global secondary index with game_id as partition key since we want to update via user_id and also retrieve via game_id. Both these options do not exists in any of the options so A seems to be nearest correct answer.

Answer D