Source: Suipiens

A few weeks back, I initiated a compilation series aimed at exploring the concept of parallel execution in blockchains. Each piece under this series will be a study of a different blockchain, explaining the mechanisms enabling it to process transactions in parallel. The first part of this series gave a comprehensible description of what serial execution is, what parallel execution is, and the different approaches to parallel execution.

Quick Recap:

Parallel Execution (PE) is a blockchain’s ability to process multiple transactions simultaneously rather than the one-by-one method (serial execution). Blockchains like Solana, Sui, Sei, Aptos, Neon, Fuel, and Monad (yet to launch) all execute transactions simultaneously albeit each with its underlying mechanism.

In this article, we will focus on Solana and how the blockchain introduced the most effective on-chain scaling method known but firstly let's take a look at off-chain scaling solutions.

When Ethereum launched with the EVM which gave it the ability to execute smart contracts, it paved the way and gave a whole new definition of what blockchain technology was capable of. However, the EVM’s design made it impossible for Ethereum to handle many transactions, making it very slow. Another limitation was the high transaction fees.

With the launch of layer 2 blockchains as a means of scaling, there was hope for the Ethereum community once more. Layer 2 blockchains process transactions off the main chain (Ethereum) and send the transaction data back. This action takes some load off the main chain, allowing it to handle other transactions and thereby reducing the risk of network congestion. However, these layer 2s have made very few changes to the two most significant challenges Ethereum faces: slow throughput and high gas fees. While layer 2s, with no doubt, offer a much cheaper gas fee as compared to Ethereum itself, these set of blockchains have been unable to solve the scalability issue as many layer 2s still take hours before a transaction is settled. Layer 2s, Ethereum, and other EVM chains are regarded as single-threaded.

Parallel Execution (PE) on Solana

In 2020, the Solana blockchain was launched after being in development for years. Founded by software developer Anatoly Yakovenko, Solana’s first block was created on March 16, 2020. The blockchain introduced its virtual machine, Solana Virtual Machine (SVM) which makes it capable of running programs (smart contracts in Ethereum). The SVM was designed to handle multiple transactions per second and this is one of the most attractive features about the blockchain. Solana boasts of processing over a thousand transactions per second. The other attractive feature of Solana is its very cheap transaction fee. It costs less than a cent to settle a Solana transaction on the blockchain.

Solana’s ability to handle so many transactions can be attributed to the Sealevel which is a component of the SVM. The following section will explain what Sealevel is and how it enhances parallel execution. Solana is the first known blockchain to introduce parallel execution.

Sealevel - the Innovative Engine Behind Solana’s High TPS

To begin, let’s dive into what SVM is. Solana Virtual Machine, like the EVM for Ethereum, serves as Solana’s execution environment. Essentially, SVM facilitates the creation of applications and protocols that we engage with regularly on the blockchain It is safe to say without virtual machines (EVM, SVM), most DeFi activities won’t be possible. The virtual machine is responsible for executing transactions, akin to mini computers.

The key component in the SVM is called Sealevel. Sealevel is the engine that facilitates "horizontal" scaling within the Solana execution environment, enabling multiple smart contracts to run concurrently without affecting each other’s performance. Solana leverages deterministic parallelization whereby it first confirms the state of the blockchain to determine the independence of transactions before parallel execution. This differs from the optimistic approach where all transactions are executed, then the dependent ones are re-executed and reverified. Solana allows transactions without conflicts to run in parallel, and because there is more probability of having more independent transactions than dependent transactions, this allows Solana to process thousands of transactions per second.

As blockchain technology evolves and developers see the importance of building products that are scalable for mass adoption, more blockchains are now exploring more approaches to enable parallel execution on-chain. In subsequent, we’ll discuss parallel execution on other blockchains and the mechanisms that make parallel execution possible on them.