Transaction stuck in mempool

Question

So 3 days ago i was sending XTZ from one cex to another and it looks like the transaction is still stuck in the mempool

hash id
onk4Rda4WacNreRM4yqHg6G89JkfChauLSynWUtoWtAt2USRTwh fee paid 0.2xtz

whats the reason for that? thanks

Answer 1

TL;DR This doesn't make much sense for the most common failures of regular tez transfers, and without further detail (e.g. like the gas limit used in the operation, the version of the Octez node used by the originating CEX, or the actual reported error), it is hard to provide more concrete answers. Best course of action is to try to re-issue the transaction or contact the CEX in question.

Long Version:

The maximal "time to live" of an operation in the mempool is adjusted to 1 human hour, currently set to 240 blocks in the Nairobi protocol.

Normally, operations whose branch (i.e the block they point to) is older than 1 hour are discarded when the mempool recycles itself, for example when the node changes heads (a new block is added to the blockchain). Except if the operation is permanently REFUSED by the Tezos protocol, in which case it's kept around longer because it is considered as spam. How longer depends on traffic and uptime as the Octez node keeps a fixed number of recently Refused operations -- 1000 by default.

Now, it is uncommon that a simple transfer operations yields such an error. Plausible causes to that would point to some internal issue with your CEX (e.g. they are not correctly crafting the transactions / signing issues). Or, maybe, it was just that the operation was briefly stuck in the mempool (e.g. for low fees) and it just continues to appear as "stuck in the mempool" in their front-end when in fact it is gone. All of these are mere speculations, which only your CEX can provide answers to.