What Is Sharding?

Sharding can improve transaction speed and scalability. Learn what the term means and how sharding works.

Key Takeaways:

• Sharding is a technique used in blockchain to enhance scalability and transaction speed by dividing the network into smaller partitions, called ‘shards’.

• Projects like Zilliqa, Ethereum, Cardano, Harmony, and QuarkChain have implemented sharding to address scalability issues.

• Sharding requires careful implementation, with challenges related to security, complexity, and tight coupling.

What Is Sharding?

In blockchain, sharding refers to a technique that divides the network into smaller partitions, called shards, to improve scalability and increase transaction speed.

In more technical terms, sharding is a form of database partitioning, also known as horizontal partitioning, where the database is horizontally partitioned into pieces (shards) to provide high concurrency and short response times. In the case of blockchain sharding, the network is split into multiple shards in which transaction validation occurs (instead of on the entire blockchain network), and each shard holds a unique set of smart contracts.

By adding shards on-demand and executing transactions in a parallel manner, the blockchain can improve its scalability, theoretically. Although this has limitations regarding power distribution, like tight coupling and other drawbacks, sharding is a sustainable long-term solution for blockchain scalability issues.

Learn more about blockchain scalability here.

Crypto Projects That Use Sharding

Zilliqa is the first public blockchain platform to have implemented sharding. The Ethereum Foundation also plans to use sharding for its Ethereum blockchain. 

Other blockchain projects using or planning to use sharding as a solution for scalability issues are Cardano and QuarkChain.

Challenges of Sharding

While sharding, at first glance, may sound like the solution to the scalability issues that plague blockchain, it unfortunately isn’t that easy.

Two main drawbacks of sharding a blockchain are complexity and security. Hackers can overtake a single shard in a segmented blockchain due to the reduced hashpower required to control individual segments. Once a segment is hacked, malicious transactions can potentially be broadcast to the leading network, disrupting the whole system.

Additionally, since different node clusters govern different blockchain segments, each shard appears as a separate blockchain network. Intershard communication mechanisms are needed to allow users and applications of one subdomain to communicate with another subdomain.

Double-Spending, Complexity, and Tight Coupling

Improper implementation can result in double-spending, which substantially affects the security of the whole network. Another challenge with sharding is its complexity. Implementing sharding on existing blockchain networks is very difficult since it involves network splits and the reassigning of state.

One key element that sharding needs is tight coupling, which is a property of sharding but not a property of sidechains. A child chain block that specifies an invalid mainchain block as a dependency is by definition invalid. More important, the mainchain block that includes an invalid child chain block is invalid.

Final Words on Sharding Blockchains

Sharding is one of several solutions to the scalability problem of blockchain. While it can massively increase transaction speed, sharding does come with its own set of challenges and precautions that need to be properly addressed.

Read more about Layer-2s, another solution to the scalability issue.

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