Blockchain Network Congestion: Causes, Effects, and How to Solve It

    Blockchains, like any other networks, can be subjected to slow performance and latency in processing transactions. Since the distributed ledger is still in its primal years, congestion is bound to take place as demand exceeds the processing capacity of the network. Blockchain network congestion can cause several issues that lead to a bad user experience, thus, putting a strain on the ledger’s mass adoption. However, this dire problem can be solved to avoid delayed transactions and high fees. 

    Let’s take a look at what blockchain network congestion is and the consequences it might lead to. 

    What Is Blockchain Network Congestion?

    What exactly is blockchain network congestion? Congestion happens when transactions pile up in a node’s mempool before being sent for confirmation. This clogs up the network as the number of pending transactions exceeds the nodes’ processing capacity to verify and add transactions to the blockchain. 

    Why would blockchain processing power not be enough to handle the increasing demand? This is the ever-long blockchain problem that is scalability. Scalability refers to a network’s ability to manage an increasing load of work, and thus increase transaction speed rate accordingly. 

    Each blockchain network has its own specific TPS (transaction per second) rate that measures how many transactions can the network process in one second. Thus, the speed of each blockchain is limited, and increasing the demand will only lead to transactions clogging up the network. 

    The Blockchain Process 

    Let’s have a quick recap of the blockchain process in order to understand the ramifications of network congestion. 

    Each transaction conducted on the blockchain first arrives at nodes’ mempools and waits as a “queued” transaction before being verified. After each node verifies a bunch of transactions, they group them into a candidate block ready to be mined and ultimately added to the blockchain. 

    However, blocks have limited sizes. Validators can’t just add an infinite number of transactions within a single block. This means that only a batch of transactions gets picked to be included in the next block, while other transactions pile up in the mempool. 

    Mempool Congestion

    What Causes the Congestion?

    There are many things that cause blockchain network congestion:

    Small Block Size     

    Each blockchain has its own block size limit that dictates how many transactions can fit in a single block. For example, the Bitcoin blockchain has a block size limit of 1 MB. This might seem insignificant, but it can hold thousands of transactions. However, if the transactions exceed the number which a single block can contain, this can lead to network congestion.            

    Small Block Size                                                  

    Increased Demand

    Blockchains are on the rise, and this can only mean an increase in demand. The more people start conducting transactions on the blockchains, the more transactions pile up in the mempool. This adds to the previous point of having a block size limit. Blockchains with very limited block sizes can have major congestion issues as demand increases. 

    Increased Demand blockchain

    Slow Block Times

    Block time refers to the time it takes the miners to verify and add a block to the blockchain. For example, the Bitcoin blockchain has a block time of 10 minutes. This heavily increases the latency of the blockchain since conducting a single transaction has a long waiting time. Waiting for the network to add one single block to the blockchains means that there is a huge timeframe where transactions can start piling up, ultimately leading to network congestion. 

    Slow Block Times

    So, What Does that Mean for Users?

    Blockchain network congestion has many effects on the network performance, thus resulting in poor user experience that can create a challenge for future mass adoption. 

    Increased Transaction Fees

    The first consequence of network congestion is the high fees users have to pay in order to get their transactions processed. When the network becomes congested, miners prioritize transactions that have a higher transaction fee. Users would then raise their transaction fees for the chance of a miner picking it up. 


    Blockchain network congestion can lead to longer transaction confirmation time which can create latency issues. Delaying the verification process can lead to delayed finality, which makes the blockchain seems inefficient. In addition, prolonging the confirmation time will lead to many transactions being stuck in the mempool for hours and sometimes days. 

    Security Risks

    Increasing the transaction fees as a result of network congestion can sometimes lead to the centralization of the mining power. This means that miners get to pick specific transactions while disregarding others. In addition, the long confirmation time can make it easier for hackers to conduct double-spending attacks

    Possible Solutions for Network Congestion 

    Blockchains are still developing, and thus, many different approaches have surfaced to solve the network congestion problem. 

    • Sharding: Sharding is a layer-1 solution that breaks down the blockchain into smaller parts known as shards that would operate simultaneously next to each other. This can increase the network processing capacity and avoid congestion. However, this can lead to some security issues.


    • Increasing Block Size: Increasing the block size is another network congestion solution but it’s a controversial one. Increasing the block limit will increase the bandwidth costs to download, upload and distribute all transactions and blocks across the network.
    • Layer-2 Solutions: Many layer-2 and offline solutions emerged to solve the congestion problem such as state channels, side chains, and blockchain rollups. These solutions can increase the network’s processing capabilities, however, they are complex to implement and can increase security issues.
    • Decreasing Block Time: A simple change of consensus mechanism can solve part of the network congestion most blockchains have. For example, Ethereum’s block time is only 13 seconds because it operates on Proof-of-Stake, while Bitcoin is 10 minutes because it operates on Proof-of-Work. 

    Network Congestion Concerns

    As long as blockchain network congestion poses a problem of efficiency, widespread adoption will not become a reality anytime soon. As more people adopt this decentralized technology, network congestion will become a dire matter that needs to be addressed. Or else, users will not adopt the blockchain for day-to-day transactions, considering the latency and long waiting time. 

    However, blockchain technology is still in its early stages and more and more solutions are surfacing that address the issue.


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