zkSync Era, the layer 2 blockchain based on zkRollups technology, went down for over 4 hours on Christmas Day due to a bug impacting the way validators calculated the network state update. We take stock of this unfortunate and ill-timed event.
Christmas breakdown on layer 2 zkSync Era
An eventful Christmas for the zkSync teams: on December 25, the zkSync Era network, a layer 2 based on zkRollups technology, came to a complete standstill for over 4 hours. Once the blockchain was back up and running, the developers of layer 2 published a post mortem aimed at clarifying the origin of the outage:
On December 25 at 05:50 UTC, zkSync Era encountered an issue triggered by one of the network’s automated safety procedures.
The issue is completely resolved, but we want to share details with the community about what happened, and what teams did to address it.
TL;DR
– There… pic.twitter.com/hO9TKlfBMQ– zkSync Developers (∎, ∆) (@zkSyncDevs) December 25, 2023
Jokingly adding that “on-call operations were particularly complicated during the vacations”, the zkSync teams explained that a bug had impacted the way operators (validators) calculated the status update, resulting in a discrepancy between the data expected by layer 1 (Ethereum) and what it received.
As a result, zkSync “went into maximum defense mode” and the sequencer had to wait for the problem to be resolved, causing block processing to stop. This security measure, described as unnecessary in the post-mortem, had been introduced when the zkSync Era mainnet was launched over a year ago, but was withdrawn following this incident.
Once the problem had been identified and resolved by the zkSync developers, the network was able to resume normal activity, and transactions that had been pending for a few hours were able to be processed normally after a reboot.
According to the developers, the problem would have been solved more quickly under normal circumstances, but the timing was such that only the on-call teams were present at the time of the incident. Finally, according to zkSync, network users’ funds were not put at risk during this unfortunate episode.
Layer 2s are becoming increasingly numerous
According to L2beat data, zkSync Era is currently the 5th layer 2 in terms of total locked value (TVL) across all technologies, behind Arbitrum, Optimism, Base and Metis Andromeda. However, zkSync Era is the second-layer network with the highest TVL in the zkRollups range.
zkSync has the distinction of being the first layer 2 to offer compatibility with the Ethereum Virtual Machine (EVM), enabling the network to take on the applications of its parent blockchain, Ethereum, and its tools such as Truffle, MetaMask and Etherscan.
Top 10 layers 2 by total locked value (TVL)
Layer 2s continue to multiply, as we’ve seen in 2023 with Base, launched by American giant Coinbase.
Thus, the “Ethereum Killer” narrative of layers 1 seems to have been forgotten in favor of solutions making use of the first smart contract blockchain instead, as the graph below shows us:
Evolution of the number of transactions per second on Ethereum (blue) and Layers 2 (red) from Nov. 2013 to today
Whatever the case, Arbitrum and Optimism, with $8.58 and $5.76 billion in TVL respectively, still dominate the layers 2 market by a wide margin. By way of comparison, Base, the 3rd largest layer 2, has “only” $740 million in total locked value.
