When the challenge of blockchain is discussed then the Scalability is in number one. It is one of the most critical challenges facing blockchain technology as it strives to become a mainstream solution for various industries. As blockchain networks grow in size and usage, ensuring their ability to handle increased transaction volumes and data throughput becomes paramount. Scalability is the blockchain's capacity to efficiently handle a growing number of transactions and users. It has to be ensured without compromising performance, security or decentralization. Solving the scalability issue is crucial for blockchain. Still there are some alternative methods.

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Most public blockchains like Bitcoin and Ethereum run as decentralized networks where every node verifies and maintains a copy of the entire blockchain. This decentralized architecture ensures that no single entity has control over the network. Although the security and trust is achived but it also results in slower transaction processing times and limited scalability. As each node must reach consensus on every transaction thus it is time consuming and lack of scalability.
To overcome this challenge various approaches have been explored to improve blockchain
scalability:

Sharding:

Sharding is a technique that involves breaking the blockchain network into smaller partitions called shards. Each shard processes a subset of transactions independently. So parallel processing and increasing the overall transaction is achieved throughput. Ethereum 2.0 is the example of it.

Off-chain Scaling Solutions:

Off-chain scaling solutions aim to reduce the burden on the main blockchain by conducting certain transactions off-chain. The Lightning Network of Bitcoin is the example of it.

Layer 2 Protocols:

Layer 2 protocols build additional layers on top of the main blockchain. It facilitates faster and more scalable transactions. Raiden Network for Ethereum and the Lightning Network for Bitcoin are two main examples of this system.
Consensus Algorithm Optimization: Proof-of-Stake (PoS) and other consensus mechanisms like Delegated Proof-of-Stake (DPoS) are more efficient & leading to higher scalability than Proof of Work (POW).

Sidechains:

Sidechains are independent blockchains connected to the main blockchain. Here the users are allowed to move assets between them. Sidechains can serve specific purposes or use different consensus algorithms.