Looking at the current results, after the gas fee on the Ethereum L1 mainnet dropped to a 5-year low, many projects feel that deploying on L1 might not be impossible, so many people ask, what core issues are L2 solving now? There is an old topic called the blockchain trilemma. According to Vitalik's explanation, it means you can only choose two out of the three: [Security], [Decentralization], and [Scalability]. Returning to the essence of technology, this is the problem L2 should solve: First, state summaries are placed on L1, maintained by the mainnet for [Security]; Second, work on the sequencer to maintain [Decentralization] as much as possible; Finally, [Scalability] is cleverly implemented off-chain by L2. Different L2 solutions have their own merits, and everyone is familiar with OP-based Rollup and ZK-based Rollup. Today, I want to talk about something different, like Based-Rollup. The Based L2 solution was also first proposed by Vitalik, and L2s like Taiko have been promoting the Based Rollup approach. PS: Note, it is Based, which has nothing to do with Coinbase's Base, which is also OP-based. As we all know, in a standard OP-based L2 system, the sequencer has a lot of power. It can decide whose transaction comes first and whose comes later, and can profit from MEV even without malicious intent. This is why, for example, Metis proposes a decentralized sequencer. Different L2s have different approaches to handling MEV: for example, Arb advocates fair treatment of MEV (strictly first-come, first-served), while OP is more encouraging, considering MEV as a free market behavior, so it taxes MEV. However, regardless of the approach, the L2 sequencer holds a prominent position. Thus, Based-Rollup chooses to cut the power of the sequencer—its philosophy is to let ETH L1 do the sequencing, thereby limiting the power of the L2 sequencer. Quoting a diagram from @taikoxyz's documentation: You can see it's a three-step process: Step one, L2 searchers package L2 transactions and send them to the L2 block Builder; Step two, the L2 block Builder constructs the block; Step three, L1 searchers include the L2 block in the block they build on L1. Here, the L1 searcher and L2 builder can be the same person. This is another clever "working two jobs" approach. In fact, the L1 searcher's equipment performance has redundancy, so building an additional Taiko L2 block is no pressure at all. To use an inappropriate analogy, if ETH and L2 are compared to the relationship between a province and a city, then the Based Rollup approach is like having the mayor (L2 builder) also serve as the deputy governor (L1 searcher), thus utilizing L1's resources to protect L2's security. It's been exactly a year since Taiko's TGE, and the Token Unlock is about to start, so Taiko has been brewing a new idea over the past year, called Based Booster Rollup/BBR. Booster Rollup can also serve as a mirror for L1, which is an interesting concept, but due to space limitations, the analysis of Booster Rollup will be expanded in the next article.