what about transactions with lower fees? I have a transaction with 5sat/byte stuck since February 11. It is not dropped from mempool, it is not being resend. Is there a chance it will be confirmed during next "low fees Sunday" ?
Only if fees drop low enough, miners include transactions that earn them most money first.
It was made in online wallet, that dont allow CPFP and RBF.
As long as they keep broadcasting the transaction, it won't drop from mempool. But if fees keep rising, and given a maximum 300 MB mempool size, the transactions with lowest fees will be dropped eventually, and in that case won't be accepted again as as long as mempool stays full.
If that happens, it's up to the service that sent the transaction to re-send it with a higher fee.
If it's a "wallet" (by my definition), it should give you access to private keys. If you have private keys, you can try CPFP. If it's an exchange or other website that doesn't give you private keys, and you sent it to a similar service that doesn't allow you to do RBF, then indeed all you can do is wait.
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