Yesterday we talked about Proof of Stake and Beacon Chain. But to truly appreciate Beacon Chain, we need to talk about sharding. The main difficulty in achieving scalability that Blockchains (including Ethereum) currently face is that every node has to verify and execute every transaction.
The Shard Chain is a scalability mechanism in which every shard ("mini Blockchain") executes its part of the transaction parallel to the other 63 shards. This means that Ethereum is split into 64 pieces of smaller Blockchains. With that many different shards, how are they going to communicate with each other? To help with this issue, there is Beacon Chain and crosslinking.
A crosslink is a reference in a Beacon Block to a Shard Block. A crosslink is a method of how the Beacon Chain follows the head of a Shard Chain. There will be 64 shards, so each Beacon Block can contain up to 64 crosslinks. When the Beacon Block has been finalized, the corresponding Shard Blocks are considered finalized too. This is needed for cross-shard communication as all Shard Chains are following the Beacon Chain at all times.
But how often the shard blocks are added to the beacon chain? As we know from the previous article, Beacon Chain has slots. A slot is a chance for a block to be added to the Beacon Chain and shards. You can imagine that the Beacon Chain and shard chains are choreographed in lockstep. Every 12 seconds, one beacon (chain) block and 64 shard blocks are added to the slot.
Phase 1 and Phase 1.5
Ethereum 2.0 will be released in multiple phases.:
- Phase 0: Beacon Chain
- Phase 1: Shard Chains
- Phase 2: Execution Engine
We already have Phase 0 behind us as Beacon Chain is operational for some time. The next steps are now focused on "The docking" of Ethereum, which means swapping the current network consensus mechanism from PoW to PoS. You can read more about it in an article I wrote 2 months ago.
Phase 1 will be the addition of Shard Chains, but there will also be something call Phase 1.5.
This phase includes a transition period from Ethereum 1.0 to Ethereum 2.0. This means the current Ethereum chain will become the first shard on Eth 2.0, so all transaction history will be available. Unfortunately, at this time, there is no exact date when this will happen.
When can we expect Shard Chains to be launched?
As we can read from ethereum.org
"Shard chains should ship sometime in 2022, depending on how quickly work progresses after the merge. These shards will give Ethereum more capacity to store and access data, but they won't be used for executing code. The details of that are still being figured out."
Everything is still a work in progress. I can recommend reading their special page about sharding to be up to date on the development.
If you look at Ethereum 2.0 as a whole, what goes into it and how much work and solving many different problems it involves. You will have a new appreciation of the hard work done by the community and developers. It's a truly wonderful time to be working in the Blockchain space and watching something like ETH2.0 being built and coordinated in a distributed way.
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