One important attribute of a good blockchain user experience is fast transaction confirmation time. Today, Ethereum has improved significantly compared to five years ago, thanks to EIP-1559 and the stable block time after the transition to PoS (The Merge). Users can generally confirm transactions sent on L1 within 5-20 seconds, similar to the experience of using a credit card. However, further improving the user experience is valuable, as some applications even require delays of hundreds of milliseconds or less. This article will explore some practical options for Ethereum to improve transaction confirmation times.
Currently, Ethereum’s Gasper consensus uses a single-slot and epoch architecture. A portion of validators vote on the chain’s head every 12 seconds, and within 32 slots (6.4 minutes), all validators have the opportunity to vote once. These votes are then interpreted into a message similar to PBFT’s consensus algorithm, providing a very strong economic guarantee called finality after two epochs (12.8 minutes). In recent years, dissatisfaction with the current method has been growing, mainly due to its complexity and the long 12.8-minute wait.
One alternative to this architecture is Single Slot Finality (SSF), which replaces the current mechanism with a consensus similar to Tendermint, where block N is finalized before block N+1 is generated. The main challenge of SSF is that it requires every Ethereum staker to publish two messages every 12 seconds, which puts a significant burden on the chain. However, there are some clever ideas to mitigate this issue, such as the recent Orbit SSF proposal, which significantly speeds up finality to enhance the user experience, without changing the fact that users need to wait 5-20 seconds.
In the past few years, Ethereum has followed a roadmap centered around rollups, where the base layer (L1) supports data availability and other features for L2 protocols (such as rollups, validiums, and plasmas) to provide users with the same level of security at a larger scale. This has led to a separation of concerns within the Ethereum ecosystem: L1 focuses on core foundational functions, while L2 focuses on directly engaging with users. However, if L2 aims to provide faster confirmation times than 5-20 seconds, a shared preconfirmation mechanism within the Ethereum scope called Based Preconfirmations is being promoted to allow all L2 (and L1) to use it.
Another architectural approach called epoch-and-slot architecture is being explored. There are three reasonable strategies for L2: based, a server with scaffolding blockchains, and a compromise approach. Depending on the application, 12-second block times may be sufficient, but for those that require faster confirmation times, the epoch-and-slot architecture may be the only solution. The design space for these approaches is still being fully explored, and having more options will lead to better outcomes for L1 and L2 users, as well as simplify the work of L2 developers.
