What is Blockchain Network Congestion?
















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What is Blockch...


What is Blockchain Network Congestion?

7 mins read / updated on Thu Nov 30 2023


Network congestion emerges when a volume of transactions overloads the network's processing capabilities, leading to an accumulation of unprocessed transactions in what is known as the "mempool." A multitude of reasons, from market dynamics to inherent network parameters like block dimensions and block intervals, contribute to this situation.

Visualize the transaction process like this: transactions are vehicles, the blockchain is a freeway, and the mempool acts as the freeway entrance. As traffic on the blockchain freeway increases, the entrance, or mempool, becomes more packed.

The capacity of the blockchain freeway is determined by elements like block dimensions and the rate of block generation. A surge in transactions, possibly due to the launch of a trending new token or a sought-after NFT series, can lead to overcrowded conditions on the blockchain freeway. An illustration is when Yuga Labs unveiled their "Otherside" metaverse initiative with an anticipated digital land sale in May 2022. While this event generated roughly $285 million for Yuga Labs, it simultaneously resulted in some of the highest transaction fees ever seen on the Ethereum platform. The rush to secure these NFT plots caused Ethereum's transaction lanes to overflow, leading to fees surpassing $176 million.

Also Read: Advantage and disadvantage of blockchain technology

How does Blockchain Technology work?

Blockchain operates as a sequence of blocks, where every block retains user-generated transaction details. Once attached to the sequence, each block is enduring and unalterable. The decentralized collection of nodes in the network maintains copies of the blockchain. With the foundation set upon cryptographic security and theoretical principles, blockchain remains the core for digital currencies such as Bitcoin and Ethereum.

Also Read: Proof of Work


It is an abbreviation for "memory pool," stands as an integral part of blockchain architecture. It acts as a transitional holding space for transactions awaiting validation and eventual incorporation into a block. When users initiate transactions within the blockchain, they're first disseminated across the network and funneled into the mempool. Depending on the blockchain's consensus method, miners (as seen in proof-of-work systems) or validators (in proof-of-stake models) cherry-pick transactions from the mempool for potential block inclusion.

Often, transactions bearing higher fees get priority, acting as an incentive. Transactions reside in the mempool until they find a block or are discarded due to expiration or invalidity. The mempool's state can fluctuate based on factors like transaction rates and block space, with surges leading to extended confirmation durations and potential fee hikes.

Also Read: Blockchain Network Congestion

Candidate blocks

Also termed proposed blocks, candidate blocks contain sets of yet-to-be-confirmed transactions and signify the next potential addition to the blockchain. Undergoing stringent validation aligned with the blockchain's consensus protocol, these blocks transition from candidates to confirmed blocks once they acquire enough validations. Notably, in blockchains with extended confirmation intervals, there's room for rival blocks to emerge during this window, potentially inducing short-lived forks or orphaned blocks.

Also Read: Smart Contracts


In the blockchain lexicon, finality denotes the irreversible state of a transaction. Once achieved, the transaction becomes an unchangeable segment of the blockchain's historical record. Different blockchain networks have nuances in their finality definitions. For instance, in the Bitcoin universe, a transaction gets a boost in finality confidence after about six additional block confirmations, while networks like Ethereum might require even more, especially with shorter block intervals. Finality's essence ensures the untampered and enduring nature of blockchain transactions, fostering trust in the system.

Longest chain principle

At its core, the longest chain principle dictates that the blockchain's genuine version is the lengthiest series of blocks, embodying the most computational effort. Temporary forks might sprout due to simultaneous block creations, but over time, the network gravitates towards the longest chain, upholding it as the true record. This principle safeguards the network's consensus, underpinning transaction history clarity and warding off malicious intents. Grasping the interplay of mempools, candidate blocks, finality, and the longest chain principle is pivotal to fathoming the occasional congestion in blockchain networks.

Also Read: Matic Bridges

Causes of Blockchain Network Congestion

A congested blockchain network emerges when the volume of transactions presented to the network surpasses the network’s capability to handle them.

Several factors can cause this congestion:

  • Increased demand: As the blockchain witnesses more transaction requests, the pool of unconfirmed transactions might grow larger than what can fit into one block. This scenario often pertains to blockchains with intrinsic constraints on block size and block frequency. This upsurge in transactions may be a result of unexpected price fluctuations initiating a burst in transaction actions or even periods of widespread adoption.
  • Small block size: Every blockchain is designed with a predetermined block size, which dictates the maximum capacity of a block. For instance, Bitcoin’s original design had a block size restriction of 1 megabyte. An enhancement, known as Segregated Witness (SegWit), was introduced in 2017 to augment transaction processing efficiency. This enhancement adjusted the potential block size to approximately 4 MB. Network congestion happens if transactions surpass this established limit.
  • Slow block times: Block time is the frequency at which new blocks are appended to the blockchain. With Bitcoin, a new block is appended roughly every 10 minutes. If there's a rapid increase in transaction creation and volume, a backlog ensues.

Also Read: Cex Vs Dex

Effects of Blockchain Network Congestion

Network congestion within blockchains can lead to a myriad of negative consequences. The most immediate consequence is extended transaction confirmation times. In intense situations, these delays can extend from mere hours to multiple days. In response to these delays, users often raise transaction fees hoping miners prioritize their transactions, leading to significant fee increases during peak times. For instance, during a surge in the Ordinals, Bitcoin transaction fees surged by 560%.

Further, congestion can compromise the reliability of a blockchain, causing potential outages or service denials. This has been a recurring issue for blockchains like Solana. Long-standing transactions in mempools can also expose the network to risks like double-spending attacks.

Also Read: BNB Validators

Managing and mitigating Blockchain Network Congestion

Tackling congestion in blockchain networks is intricate, and various strategies exist, each with its strengths and pitfalls.

  • Increasing block size: By amplifying the block size, a greater number of transactions can be accommodated in each block, which in turn raises the throughput. However, these enlarged blocks take more time to disperse across the network, elevating the chances of temporary splits. Additionally, this requires more storage, potentially centralizing the network.
  • Decreasing block time: Minimizing block time accelerates transaction processing. Yet, shorter intervals might raise orphaned block instances, jeopardizing security.
  • Layer 2 solutions: These are auxiliary platforms that handle transactions off the principal blockchain, registering only the final outcomes. Examples include Bitcoin's Lightning Network and Ethereum's Plasma. While they boost scalability, their implementation is intricate and could pose new security challenges.
  • Sharding: In sharding, a blockchain fragments into smaller segments or shards, each processing its transactions and contracts. This effectively multiplies a network's processing ability. But like Layer 2 solutions, sharding introduces complexities and potential security concerns.

Alternative approaches encompass adjusting fees, scaling through techniques like optimistic and zero-knowledge rollups, and considering faster consensus mechanisms like Proof of Stake (PoS) over Proof of Work (PoW).

Also Read: Proof Of Work Vs Proof Of Stake


The dilemma of blockchain network congestion arises when transactions overflow the processing capability of the network. This overflow can lead to prolonged transaction validations, skyrocketing transaction fees, and diminished user satisfaction, potentially stalling the uptake and functionality of blockchain networks.

Several remedial measures, ranging from augmenting block size, slashing block time, and initiating layer 2 solutions to experimenting with sharding, are under exploration. Each remedy offers its unique benefits and obstacles, and the preferred choice is contingent on the distinct needs and limitations of the blockchain network.

Although network congestion presents formidable challenges, it also spurs inventive solutions in the blockchain domain. As the technology evolves and yields more efficient solutions, we anticipate blockchain networks will attain greater scalability and efficiency, further bolstering their transformative potential across diverse economic sectors.

Frequently Asked Questions [FAQs]

Q: What is blockchain network congestion?
A: Blockchain network congestion occurs when the number of transactions submitted to the network exceeds its capacity to process them. This can lead to delayed transaction confirmations and an increase in transaction fees.

Q: Why do blockchain networks experience congestion?
A: Blockchain networks can experience congestion due to various factors including increased demand from users, inherent limitations in block size and block time, sudden price volatilities, and waves of mass adoption cycles.

Q: How does high transaction volume contribute to congestion?
A: High transaction volume increases the number of unconfirmed transactions in the mempool. If the number of transactions in the mempool exceeds what can be included in a single block due to block size limitations, the network becomes congested.

Q: What role does limited block size play in network congestion?
A: Each blockchain has a block size that defines the maximum size a block can be. This block size limits the number of transactions that can be included in a block. If the number of submitted transactions exceeds this block size limit, it results in network congestion.

Q: Can smart contracts cause blockchain congestion, and if so, how?
A: Yes, smart contracts can cause blockchain congestion. When a smart contract is executed, it may involve multiple operations and generate several transactions. Especially in platforms like Ethereum, where smart contracts are prevalent, a popular or complex contract can generate high transaction volumes, leading to congestion.

Q: What are the common effects of blockchain network congestion?
A: The common effects of blockchain network congestion include increased wait times for transactions to be confirmed, exponential increases in transaction fees, potential downtimes, and increased vulnerability to certain security risks, such as double spending attacks.

Q: How does congestion lead to delayed transactions?
A: Congestion causes a backlog of transactions in the mempool as there are more transactions waiting to be included in blocks than the network's capacity. With limited space in each block, transactions can end up waiting for longer periods before getting picked up and included in a block.

Q: Why do transaction fees increase during network congestion?
A: During congestion, users often increase their transaction fees to incentivize miners to prioritize their transactions over others. As everyone competes for a spot in the next block, this competition can lead to exponential fee hikes.


Zainab Saberi

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