should help you out I am not pretending, but after a lost day, i finally came up with a solution which workaround this. I cannot say if it is a feature or just a problem to report. Anyway in Hazelcast if you put in an IMap a value as ArrayList thus will be Serialized Entry By Entry. Which means if we have 100 entries of the same instance A which is 6K we will have 600K with Hazelcast. Here a short RAW code which prove my answer.