Is a composite key prone to hot partition?

Let's say I have an items of

Item 1 - PK: userId1, SK: chatRoomId1
Item 2 - PK: userId1, SK: chatRoomId2

Now, I understand we have a 1k wcu/s hot partition limit. Modifying Item1, 1k times in a second would give us a hot partition issue. But what if we modify Item1 600 times, and Item2 600 times as well in a second.

Despite both items being in the same partition key but different sort key, would we still encounter hot partition issue?

Answer

DynamoDB can split partitions down to the size of a single item, so while you might have a hot partition initially because the two items shared the same partition key and started in the same partition, the database would adapt quickly.

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