Document the need to disable mempool cache
To prevent old transactions from being replayed, CheckTx must implement replay protection.
Tendermint provides the first defence layer by keeping a lightweight in-memory cache of 100k ([mempool] cache_size) last transactions in the mempool. […]
There are cases where a transaction will (or may) become valid in some future state, in which case you probably want to disable Tendermint’s cache. You can do that by setting [mempool] cache_size = 0 in the config.
Since Ercoin provides its own replay protection and falls into the case described in the last paragraph, nodes should set mempool cache size to 0. This should be documented (and possibly automated).