What Is an Optimistic Rollup?

Last Modified:
February 28, 2024

When so many users try to transact on a blockchain network at the same time, the network may not be capable of processing all the transactions at once. This is especially true of slower networks like Ethereum, which can only complete around 15 transactions per second.

When the network is busy, transaction fees — also called gas fees — go up. If users want their transactions to push through immediately, they need to pay higher gas prices, which can reach up to hundreds of dollars if the network is crowded and too many people are transacting at the same time. Otherwise, they will need to wait for a long time until their transaction request can be accommodated by the network.

To avoid network congestion, several scaling solutions have been developed to increase the number of transactions a blockchain can complete every second.

A rollup is a type of scaling solution used to speed up a blockchain by completing transactions outside the blockchain and recording the results on the blockchain afterward. Rollups can speed up the number of transactions per second by up to a hundred times faster than average. There are two main types of rollups: ZK-rollups and optimistic rollups.

Image Source: Dappradar.com

Optimistic rollups generate and validate transactions outside the main blockchain, and group them into batches of data. Each batch is then published as a single entry on the main blockchain. This saves time, space, and gas fees, and makes the blockchain network more efficient.

The reason why these rollups are called “optimistic” is because when the batch of data is being published on the main blockchain, the network automatically assumes that all the information is correct, and does not require additional steps to verify it. Unfortunately, because the main blockchain does not check the accuracy of all the transactions, there is a chance that some of them may be incorrect.

Overall, optimistic rollups help solve the problems of blockchain accessibility and convenience. Check out our other guides to learn more about other blockchain problems and ways to solve them. Happy learning, Ka-Bit!