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It's the combination of intelligent communication and signaling of changes in external data sources. The beautiful thing is none of it depends on Hive and vice versa.

The max size is around 8kb but that would be frowned on. The larger the custom json, the higher the RC cost. We just don't need to say a lot.

But even if we want to , then it would still not be very big investment to have sufficient RC to do that 8kb message right ? I mean, it would still be far cheaper than any other transaction on ETH or BTC ?

The 8kb is a limitation from block size. There is another limitation that one single account can only put 5 custom_jsons in one block (every 3 seconds).

Using Hive as a SQL database is not going to work. Designing around Hive is something that needs to be carefully thought out.

"kb" as KB (kilobyte) or Kb (kilobit)? Either way, a good amount of message can be stored in 8 kb. An SMS can be 140 bytes (0.14 Kilobyte) (1120 bits) (160 7-bit characters).