Blockchain Explorer By Bitquery https://www.instapaper.com/p/16800704 So, if there is a large number of transactions in the mempool and you compensated a relatively lower transaction cost, your transaction can keep on being unconfirmed for an prolonged period of time considering the fact that miners/validators will select transactions with bigger service fees https://k12.instructure.com/eportfolios/1098588/entries/3707785