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The Mempool Accelerator helps expedite stuck Bitcoin transactions by allowing users to pay a higher fee to miners. It offers a transparent service alongside alternative methods like Replace By Fee (RBF) and Child Pays for Parent (CPFP) for managing unconfirmed transactions.
Bitcoin transaction stuck in limbo? Don’t fret, the Mempool Accelerator is here to help. Why do some transactions go unconfirmed? Well, the Bitcoin network is a real free market and a very dynamic one at that. An unfortunate effect of these characteristics is that users sometimes offer a low fee as the demand for block space grows. That congestion causes a rise in fees and, in turn, miners don’t find the transaction as attractive as others and don’t include it in blocks.
What to do if the network is congested and the user’s transaction remains unconfirmed?
Blink already defined the mempool concept, and in that article we said, “If a transaction doesn’t offer a competitive fee, sometimes it gets stuck in the mempool. Besides waiting for it to disappear and taking the associated risks, a user has two options.” More on those two options later, for now, Blink wants to present a third fee-bumping technique. According to its creators, “Mempool Accelerator™ is a service to get your stuck transactions confirmed by paying an out of band fee.”
Let’s unpack that.
If the Bitcoin network is an actual free market, arguably the first the world has ever seen, then the Mempool Accelerator’s ways are valid. That being said, Rhett Reisman describes an out of band fee as:
“If you found the people who are mining the next block, you could bribe them in cash to include your transaction in that block. In fancy bitcoin terms, we call this an "out-of-band" payment.”
The Mempool Accelerator team describes their process in a more favorable light:
“Mempool sends your acceleration request to our mining pool partners. Partners who choose to accept your acceleration request prioritize your transaction based on your new accelerated fee rate.
For example, if you use Mempool Accelerator™ to accelerate a 1 sat/vB transaction to a 20 sat/vB target fee rate, mining pool partners will treat the transaction as though it has a 20 sat/vB fee rate.”
It’s also worth noting, and this characteristic is crucial, that everything the Mempool Accelerator does is transparent and public.
“Recent accelerations can be seen on the recent accelerations page or fetched using the public API.
The additional fees paid to increase the priority of the transaction are displayed on each block page.”
With that clear, let’s keep our promise.
The Bitcoin network offers two fee-bumping routes embedded in the protocol. And make no mistake, even its creators consider the Mempool Accelerator a last resource tool:
“You should always use RBF or CPFP if you can, and if it makes sense for your use case. If you cannot use RBF, or it doesn’t work for your use case, Mempool Accelerator™ is available as an option to bump your fee.”
Let’s quickly explore the other two options.
Users can replace a transaction stuck in limbo with another one with higher fees if all the conditions are present. What are those conditions? The new version of the transaction must have the same inputs as the unconfirmed one, plus, according to River Learn:
“RBF only works while the transaction is in the mempool. As soon as a transaction enters a block, it cannot be replaced by fee. Additionally, when a transaction is first sent, it must specify that it is available to be replaced by fee.”
That’s right, the user has to activate Replace By Fee in the original transaction. Not only that, not all wallets support RBF. If any of these conditions are not present from the beginning, the Mempool Accelerator might come in handy.
This hilariously named option is clever. A recipient with an unconfirmed transaction in the mempool might just create a second transaction that spends the Bitcoin stuck in limbo. This new transaction offers a higher fee, but to process it, the miner has to also process the first one.
Since the sequence of events might be confusing, let’s quote how River Learn puts it:
“The recipient may create a new transaction spending the bitcoin they received in the previous transaction (even though it is still unconfirmed in the mempool). This second transaction will pay a higher fee and signal to miners that they must mine the first transaction first in order to mine the second transaction.”
The tricky part here is that the recipient is the one who’s in position to make this happen. For the sender to solve the situation, the Mempool Accelerator might be necessary.
As you might expect, a deluxe service like the Mempool Accelerator comes with a price tag. And, of course, the creators accept BTC, both on-chain and through the Lightning Network. To process the payments, they use BTCPay Server and to collect through the Lightning Network they use the Blink API.
Interoperability and interconnection, that’s the Bitcoin way.
