Blockchain congestion: causes, consequences, and solutions

When the flow of vehicles becomes too heavy, a traffic jam forms on the road. A similar situation occurs with a blockchain when the number of simultaneously active users exceeds the network's throughput capacity. In this case, the blockchain network becomes congested.

What is blockchain network congestion?

Blockchain congestion occurs when the flow of incoming transactions exceeds the capacity of the block being added to the distributed ledger.

Problems associated with blockchain congestion remain relevant not only for early networks such as Bitcoin and Litecoin, but also for next-generation decentralized protocols that use more efficient consensus mechanisms.

Causes of blockchain network congestion

High transaction volume

As the definition shows, one of the main causes of blockchain congestion is a large volume of transactions sent to a decentralized protocol simultaneously.

This leads to one of the key blockchain-related problems: the lack of scalability. First-generation networks such as Bitcoin and Ethereum (before The Merge upgrade in 2022) were not adapted to users' growing needs, which regularly resulted in blockchain congestion.

A sharp spike in user activity causes blockchain congestion for various reasons. For example, at different times, blockchain network congestion was caused by:

One of the first blockchain games, CryptoKitties, on Ethereum, which became extremely popular;
The boom in initial coin offerings (ICOs) on the Ethereum blockchain;
The launch of the Trump token on Solana in 2025;
MEV bots in the Solana ecosystem;
The launch of Ordinals on the Bitcoin blockchain.

Long block generation time and limited block capacity

Blockchain network congestion can also occur because a decentralized network block has a limited size and can accommodate only a certain number of transactions. When this limit is exceeded, blockchain congestion occurs. For example, a single Bitcoin block can contain only up to 2,700 transactions.

In addition to having a limited size, a block also has a completion time, which differs across blockchains. For example, in the Bitcoin network, a new block is created every 10 minutes, while in Solana, finalization takes only 400 ms, making the network significantly more efficient and resistant to congestion.

Block size and block creation speed directly affect network throughput, which is measured by the number of transactions per second (TPS). For example, Bitcoin can process around 7 transactions per second, while Solana can process approximately 1,500–4,000. The higher this figure, the more operations the network can process simultaneously and the lower the risk of blockchain congestion.

Inefficient consensus mechanism

The Proof-of-Work (PoW) consensus mechanism built into Bitcoin provides a high degree of decentralization but is highly resource-intensive and scales poorly.

More modern consensus mechanisms, such as Proof-of-Stake (PoS) and its variations, do not require energy-intensive computations to add new blocks. This allows blockchains to reach agreement on the network state faster and reduce transaction confirmation times.

As a result, PoS-based networks can often process more transactions per unit of time, meaning blockchain congestion may occur less frequently or require a significantly higher network load.

Complex transactions

In blockchains that support smart contracts, certain operations may require significantly more computational resources than a regular funds transfer. For example, a single transaction on a decentralized exchange may involve interaction with several smart contracts at once and the execution of numerous internal operations.

As such applications become more popular, the load on the network increases. If the available computational resources and blockchain throughput are insufficient, blockchain congestion occurs: transactions remain pending for longer periods, while fees may increase.

What does blockchain congestion lead to?

The larger the volume of incoming transactions compared with the network's actual throughput capacity, the more severe the blockchain network congestion will be and, accordingly, the more significant its consequences.

In the case of minor blockchain congestion, transactions may experience only slight delays, resulting in an overall slowdown of the network.

In addition, if the transaction fee is too low during blockchain congestion, a transaction in the Bitcoin protocol may fail to be confirmed altogether, meaning that it may remain "stuck" for an indefinite period.

As a result, users must increase fees to speed up transactions. As a result, during periods of peak demand, fees on the Bitcoin network increase significantly and may reach tens of dollars.

The same situation occurs on other blockchains and is related to the fact that miners prioritize transactions for which users have paid higher fees. For example, in January 2025, amid the launch of the official TRUMP memecoin, fees on the Solana network surged by more than 800%, clearly illustrating the consequences of blockchain congestion.

In the case of more severe blockchain congestion, delays can become extremely long. For example, during peak congestion, Bitcoin transaction processing times can reach several days.

Analysts identify blockchain congestion as one of the most common causes of decentralized network outages. This has already happened with Ethereum and Solana.

In 2017, the hype around non-fungible tokens (NFTs) and the widely discussed CryptoKitties game caused such severe blockchain congestion on Ethereum that it nearly brought the network to a halt.

And in May 2022, the Solana network was unable to cope with an influx of bots, which caused severe blockchain congestion and ultimately led to the network shutting down. As a result of the blockchain congestion, Solana did not produce new blocks for around seven hours.

What solutions are proposed for blockchain congestion?

Layer 2 solutions

To eliminate potential blockchain congestion, developers launch separate networks that operate on top of the main network as a second layer. This helps reduce the load on the underlying blockchain.

Layer 2 solutions, such as Polygon and Arbitrum for scaling Ethereum, allow transactions to be processed outside the main network and then confirmed in "batches" on the Layer 1 blockchain. This approach helps reduce blockchain network congestion.

Sharding

Sharding is a mechanism that divides one network into several segments, or shards, that can process transactions in parallel.

With this mechanism, the network can distribute transactions across individual shards, helping avoid blockchain congestion.

Transaction batching

Another solution to the problem of blockchain congestion is transaction batching. This makes it possible to reduce the load on the network and lower fees, which increase along with user activity.

A similar mechanism, for example, was proposed as part of the account abstraction concept implemented on the Ethereum network. This approach makes it possible to turn complex transactions into a single simple transaction.

Increasing block size and reducing block production time

The larger the block size and the shorter the time required to produce it, the higher the network throughput and the stronger its resistance to blockchain congestion.

Larger block sizes have been implemented in the Bitcoin Cash and Litecoin blockchains, which can process more transactions compared with Bitcoin.

Blockchains such as Solana, Avalanche, and Cardano have reduced block production times, creating new blocks every few seconds or faster. For example, after the Alpenglow upgrade, block confirmation time on the Solana network decreased to 100–150 ms.