Hello @Jackie As per this conversation, each primary key took about 240 Bytes. But according to this doc, the total memory usage by upsert is roughly

(primaryKeysCount * (sizeOfKeyInBytes + 24))

.May I know how accurate this estimation is ?

Good call. The value in the doc doesn't count the overhead of entry object in the map, and the object wrapper size should be included as the

primaryKeysCount

. In reality, there are more than 100B overhead per entry stored in the ConcurrentHashMap

that's a good pragmatic summary of Alex Shipilev's blogs. 👍