On May 23rd, Ethereum co-founder Vitalik Buterin wrote that "Layer2" and "sharding" are often described as two opposing strategies for blockchain scalability in public discussions. However, when you delve into the underlying technology, you will find a puzzle: the actual scaling methods are completely the same. Both have some form of data sharding, fraud proof or ZK-SNARK proof, and a method for solving cross-{rollup,shard} communication. The main difference is who is responsible for building and updating these parts and how much autonomy they have.

A Layer2-centric ecosystem technically realizes sharding very realistically, but this is a sharding that can create its own rules. This is very powerful and can inspire a lot of creativity and independent innovation. But it also has key challenges, especially in terms of coordination. For a Layer2-centric ecosystem like Ethereum to succeed, it needs to understand these challenges and address them positively, in order to gain as many advantages as possible from the Layer1-centric ecosystem and get as close as possible to having the best features of both.