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Can Ethereum Scale?
“Scalability” is one of the toughest problems for cryptocurrencies, including the second-largest by market cap, Ethereum. In short, developers and enthusiasts want the cryptocurrency to support as many users as it can. Right now it can’t support very many – just a few transactions per second, which isn’t very much compared to Visa, Facebook and other apps Ethereum’s developers hope the cryptocurrency will ultimately compete with.

Ethereum is a cryptocurrency platform that uses smart contracts – rules that execute automatically exactly as written. Ethereum advocates hope the platform will give users more control over their online data. With traditional apps and services, the platform owners have a window into much of what their users do online. For example, Gmail has a copy of all of its users’ emails, and Twitter habitually bans accounts that don’t follow its rules. Ethereum is a platform for building applications similar to the apps we use today, but without centralized control.

Providing a decentralized alternative to tech platforms has challenges. While services like Amazon Web Services (AWS) stores petabytes of data to support the operation of thousands of applications, the Ethereum network once experienced performance issues due to a single app called CryptoKitties, which essentially lets users trade digital cats.

That’s because blockchains like Ethereum are fundamentally different from server-based models; they’re highly specialized peer-to-peer networks that require thousands of volunteers from around the world to store a copy of the entire transaction history of the network. This is a big task – one traditional apps don’t have to contend with.

Ethereum manages this issue partly by requiring apps that run on the network to expend Ethereum tokens, called ether, to perform tasks. These transaction fees, sometimes called “gas,” are set by Ethereum miners and vary directly with activity on the network. When many Ethereum-backed cryptocurrencies spiked in popularity in the summer of 2020, the corresponding fees rose greatly.

Why is scaling Ethereum so difficult?
Instead of having a central authority, Ethereum depends on a network of volunteers running “nodes,” each of which stores the entire transaction history and the current “state,” consisting of all of the account balances, contracts, and storage. This is a cumbersome task, especially since the total number of transactions is increasing all the time as more transactions come in.

To make sure the network is decentralized, it should be as easy as possible for as many people as possible to run these nodes. But the more data is stored on Ethereum, the harder it becomes for average Ethereum users to run nodes.

So if, say, Ethereum’s developers decided to allow users to post unlimited data to the platform, each node would balloon to a size that the average enthusiast wouldn’t be able to accomodate. Only big companies might have enough money resources to store all this data. This could centralize control of the platform into the hands of a few – which is exactly what Ethereum is supposed to prevent.

This limitation of Ethereum and other blockchain systems has long been discussed by developers and academics. Researchers have been exploring technologies for getting around the limitation for years, some of which will fall into the coming upgrade, Ethereum 2.0, which officially began rolling out on Dec. 1, 2020. Ethereum’s top developers say changes will gradually be phased in over the coming years.

The big caveat is that no one knows ahead of time how successful these upgrades will be, nor how many people the system will successfully support once the series of upgrades are in place. The upgrade has its fair share of skeptics.

Here are the most-discussed scaling techniques in the Ethereum pipeline.

Ethereum rollups
Rollups are expected to be the Ethereum scalability technique to arrive in the short term. Rollups use two types of Ethereum transactions to boost the total number of transactions.

There are two types of Ethereum transactions:

On-chain transactions: A limited, expensive type of transaction. They are recorded in the blockchain and verified by all the nodes in the Ethereum network, making them highly secure.
Off-chain transactions: Are not recorded in the Ethereum blockchain, but are tied to it nonetheless, so that the type of transactions makes many of the same security guarantees.
Rollups make it possible for a single on-chain transaction to handle a series of secure off-chain transactions. The on-chain transaction “rolls up” the off-chain transactions, so to speak, using the on-chain transactions more efficiently.

There are two types of rollups:

Zk-rollups: These use zero-knowledge proofs, a relatively new cryptographic technique used to prove that some information exists, without revealing what the information is.
Optimistic rollups: These rollups rely on financial incentives for their security instead of cryptography. Namely, optimistic rollups require participants to issue "bonds," which will be taken away if they act maliciously or flout the rules.
Rollups are seen as a short-term way to push Ethereum scaling to new heights, and are expected to be rolled out over the next couple of years. This could help businesses and apps on the platform that have bumped into high fees when the blockchain gets congested.

In 2020, Ethereum creator Vitalik Buterin published a roadmap with rollups at the center.

Sharding Ethereum
Sharding could provide more dramatic scalability.

As mentioned before, right now each Ethereum node needs to store the state of each and every account on the network. Sharding would change that by drawing from a time-honored computer scaling technique called “database sharding,” which breaks a database into more manageable pieces.

The goal of sharding is to move away from requiring users to run “full” nodes – those which store the full state of the network and every transaction that occurs. Instead, each node stores a fraction of this data and only verifies those transactions.

If a node needs to know about transactions or blocks that it doesn’t store, then it finds a node that stores the information it needs. This is where things start to get tricky. The problem Ethereum developers have faced here is that the process isn’t trustless – a defining characteristic of blockchains — since, in this model, nodes need to rely on other nodes.

Ethereum developers are looking to solve this problem using “cryptoeconomic incentives” that drive users of a system to act a certain way – in this case, ensuring that nodes are passing on valid information to other nodes.

New types of Ethereum transactions
Another capacity-expanding technology borrows from Bitcoin’s Lightning Network, a proposed top-layer upgrade to Bitcoin that is meant to address its own scaling issues. Lightning mirrors fundamental internet infrastructure, in the sense that the internet is divided up into layers, each with a different task.

According to this vision, most transactions will be made on off-chain micropayment channels, lifting the burden from the underlying blockchain.

Plasma, TrueBit, and Raiden are a few examples of this technology. But they each have a different goal in mind. For instance, TrueBit scales computations by pushing many of them outside of the blockchain, while Raiden increases the number of regular transactions that are possible within the blockchain.

The reason these techniques would work, in theory, is that either party can kick the transaction back to the blockchain anytime they want, giving both parties the ability to end the interaction.

Ethereum scaling FAQs
Why do people run Ethereum nodes in the first place?
Despite the inconvenience of setting up a node, running one provides a user with boosted security and privacy. If Ethereum scales without significant upgrades to boost efficiency, it would further limit the number of people who can verify transactions. In addition, some argue it’s good for the broader Ethereum network. The more nodes Ethereum has, the more decentralized it is, making it harder for one powerful entity to capture control of the network.

What happens if Ethereum nodes have to store ever-greater amounts of data?
The worry is that, if developers raise the size of each block to fit more transactions, the data that a node will need to store will grow larger – effectively kicking people off the network. If each node grows large enough, only a few large companies will have the resources to run them.

In other words, decentralization and scalability are currently at odds, but developers are hunting for ways around this.

How long will it take for Ethereum to scale?
This is unknown. There’s still a lot of experimentation happening on the scaling front.

In sum, although Ethereum currently can only handle a handful of transactions per second, its architects have high hopes for the future. In creator Vitalik Buterin’s words, the long-term goal is for the platform to be able to process transactions at “Visa-scale transaction levels” or beyond.

Why does Ethereum sometimes have higher fees?
There’s a limit to how many ether transactions can be sent at once. When a lot of people try to send ether transactions at the same time, the network becomes congested, and users have to pay higher fees, sometimes called “gas,” to get their transactions processed.