From my understanding, there is a bit of state which is held on a node when interacting with it over JSON RPC. One of these states local to the node is the txpool. The txpool is exposed with the
web3.eth.getTransaction(txHash) method. It returns a transaction where
transaction.blockHash == null if the transaction is in the txPool and returns
transaction == null when the transaction is unknown.
sendTransaction call is made to one node followed by a
getTransaction call to another node, with the transaction hash returned from
sendTransaction, a null transaction will be returned because the transaction is only in the first node's txpool and the second node knows nothing about it.
What do services like myetherwallet do to ensure that sessions are maintained across requests so things like this don't happen? Is there a way to synchronize the transaction pools?