Understanding blockchain Sharding in 3mins.

Welcome to Intro to Crypto; my 20-part series explaining blockchain and crypto in simple, granny-friendly English.

In The world's simplest explanation of Blockchain,  I explained that a blockchain is just a ledger (or 'list') of payments  ordered by time. Your bank uses the same sort of thing to keep track of  your money; a spreadsheet with 3 columns: money in, money out and final balance. Very simple.

All together now

The main difference with a blockchain is that everyone has copy of the same ledger so nobody can cheat. The problem is 'how do you get them to update their ledgers at the same time?' Because payments are processed batches (or 'blocks') you have to wait until your payment is picked up by the network.

And when there's tens of thousands of payments every second, blocks get full and waiting payments (or 'pending transactions')  pile up. Think of it like a 20-storey building with 700 people but only  3 elevators. Inevitably, a lot of people will be waiting on the ground  floor for quite some time. It's the same with a blockchain agreement (or  'consensus').

One solution to this problem is called 'Sharding'.

A good way to think of Sharding is like the formation of the United States.

The  US has a collection of federal laws that are upheld all over the  country. These are some of the most important laws like 'no drunk  driving'. But because the country has so many citizens, it's hard to get  people to agree on the smaller things. So the country was divided into  50 States.

These 50 States can make, update and uphold State laws  without consensus from other States. In this way, things get done  quicker and people are happier.

This is similar to how Sharding works on the blockchain.

A  single blockchain has one set of rules for the whole network. These are  some of the most important rules, like whether it's running Proof of  Work or Proof of Stake. But because the network has so many members, it  takes time for everyone's ledger to sync. So the network is divided into  mini blockchains, or 'Shards'.

These Shards can  process and update their part of the blockchain without consensus from  the other shards. In this way, payments get processed quicker (because  shards are working in parallel) and users are happier.

Shattered dreams?

The  good thing about current blockchains is that attacking them (to spend  the same money twice) is expensive. To do it, your computer needs to be  as powerful as more than half the computers on network, which for a  blockchain like Ethereum is usually thousands of computers.

With  Sharding, there's only a few computers per shard so it's easier to  attack. The good news is, this is harder to do in Proof of Stake than  Proof of Work. Ethereum founder Vitalik Buterin has announced plans to  switch Ethereum to Proof of Stake before using Sharding to scale the  network.

We don't know if it'll work exactly as planned but it  looks like Sharding holds huge promise for the future of speeding up  blockchains.

Wanna know more? I recommend this video on Sharding.

More quick explainers from the world of blockchain…

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