What Is Parallelization and How Does It Work?
What Is Parallelization and How Does It Work?

What Is Parallelization and How Does It Work?

Published May 10, 2024Updated Jun 21, 2024

Key Takeaways

  • In the blockchain space, parallelization is a method of processing multiple transactions at the same time.

  • There are various types of parallelization, including transaction-level parallelization, block-level parallelization, and smart contract parallelization.

  • Some benefits of parallelization include faster transaction processing, improved scalability, and reduced gas costs.


Efficient transaction processing is key to improving the throughput of blockchain networks and resolving the blockchain scalability problem. In this article, we will explore the basics of parallelization, how it works, some of the common types, and potential benefits.

What Is Parallelization?

Parallelization (Parallel Transaction Execution) is a method of processing multiple tasks at the same time. Parallelization is closely related to parallel computing, which is a concept in computer science that refers to the simultaneous execution of multiple processes.

How Does Parallelization Work?

Parallelization organizes the network data in a way that enables the validation of multiple transactions simultaneously instead of processing them sequentially (one by one). The task of executing transactions is distributed across several nodes. Each node handles different segments of the transaction load, which facilitates faster processing times and reduces network congestion. 

In parallel transaction processing, the network simultaneously examines numerous possible states, each illustrating the consequences of validating a specific group of transactions. This allows the network to assess the potential impact of transactions before they are officially recorded on the ledger. Following this evaluation, nodes agree on a common state that mirrors the collective outcome of these parallel validations.

Parallelization models

There are two main types of blockchain parallelization: optimistic parallelization and state-access parallelization.

1. Optimistic Parallelization. In the optimistic parallel execution model, the network skips the initial sorting phase and directly processes transactions concurrently. This approach presumes that most transactions in the queue are independent and employs a method to revisit and correct any transactions found to be interdependent post-execution. This means that if transactions are initially thought to be unrelated but are later found to affect each other, the system will adjust them to ensure all data remains accurate.

2. State-Access Parallelization. The state-access parallel execution model starts by categorizing transactions according to their effects on the network's state, such as interactions with particular smart contracts or accounts. This helps identify transactions that can be processed in parallel without conflict. Transactions that do not interact with each other are executed simultaneously. Conversely, transactions that affect similar state elements are processed in a specific order, with prioritization based on gas fees.

Different Types of Parallelization

Transaction-level parallelization

Transaction-level parallelization allows for the simultaneous processing of multiple transactions. This increases the network's throughput, enabling a higher number of transactions per second (TPS). It also reduces the time needed for transaction confirmations, improving the overall responsiveness of the network. This type of parallelization is particularly valuable for high-demand blockchains where maintaining quick processing times is important. 

There are also some challenges associated with transaction-level parallelization. For instance, processing transactions concurrently can create data dependencies, where the output of one transaction might influence another, requiring complex data management strategies to ensure consistency and reliability.

Block-level parallelization

Block-level parallelization involves the concurrent creation and validation of blocks, aiming to improve network scalability. By processing multiple blocks at the same time, this approach helps the blockchain accommodate more transactions and prevent potential network congestion. 

However, block-level parallelization requires careful implementation to avoid compromising the security of the blockchain. Moreover, block-level parallelization demands more computational resources, which raises the hardware requirements for network nodes. This could potentially limit the ability of some users to participate in the network, negatively affecting its decentralization and accessibility.

Smart contract parallelization

Smart contract parallelization refers to the parallel execution of multiple smart contracts. This can improve the performance of decentralized applications (DApps), enhancing their scalability and responsiveness.

Several mechanisms facilitate the parallel execution of smart contracts. For instance, optimistic rollups execute transactions off-chain and only interact with the blockchain to finalize them, reducing the load on the main chain. Ethereum’s Validium scaling solution combines zero-knowledge proofs with off-chain computation, providing both scalability and privacy for smart contract applications.

Benefits of Parallelization

High transaction processing speed

The distribution of tasks across multiple nodes decreases transaction execution times, which boosts the transaction processing speed. Networks that utilize parallelization tend to be more efficient than those operating on sequential processing models.


Parallelization tackles the blockchain scalability problem by spreading transaction validation across different nodes. This speeds up the process and supports horizontal scaling. Horizontal scaling allows the network to add or remove nodes based on demand fluctuations.

Reduced gas costs

Parallelization reduces fees by allocating transactions to node subgroups. This is less costly compared to sequential processing, where each transaction is validated by every node. Furthermore, faster transaction speeds decrease the competition between nodes, driving down transaction fees even further.

Closing Thoughts

Parallelization is a method of processing multiple transactions simultaneously. It offers many benefits, including higher transaction processing speeds, improved scalability, and reduced fees. In the future, parallelization can be combined with other scaling solutions, such as sharding, to achieve even greater scalability in blockchain networks.

Further Reading

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