What is the limit of the database size given dust protection measures announced by the IOTA Foundation?
Assuming an unrealistic worst case where every IOTA address would contain exactly
1'000'010i, split into on 1Mi dust allowance transaction and 10 1i dust transactions, and assuming that every output was sent in its own distinct transaction (e.g. everybody moved his received iota after he received it to a different address).
In this case, with a circulating supply of 2779530283277761i, there would be a total of 2779530283277761/1000010*11 transactions, which are 30574527370 or slightly above 30.5 billion transactions.
For each transaction, the database must store 32-byte transaction id, 32-byte address and some smaller metadata (amount, output index) which should fit into 8 byte, so 72 bytes total.
All in all, the total size would be about 2 TiB.