Rollups Breakthrough: The Core Solution for Ethereum L2 Scaling

When we talk about the future of Ethereum, one word almost cannot be avoided—Rollups. This is not an accidental popular term, but a carefully considered technical direction confirmed by the Ethereum community. In simple terms, Rollups are a Layer 2 scaling solution that is becoming a key to solving the congestion problem of the Ethereum network.

Why Does Ethereum Need Rollups Technology

All blockchains face the same dilemma—the “Blockchain Trilemma.” This triangle includes three vertices: decentralization, security, and scalability. In reality, almost no blockchain can achieve all three simultaneously. Ethereum’s choice is clear: it prioritizes decentralization and security but makes compromises on scalability.

Where is this reflected? It can only process 15 transactions per second (TPS). In comparison, traditional payment systems can handle thousands of transactions per second, so Ethereum’s speed obviously cannot meet the growing demand. When transactions pile up and the network is congested, Gas fees soar. Users compete by bidding higher Gas fees to prioritize their transactions, ultimately making using Ethereum an expensive affair.

This directly contradicts Ethereum’s original intention—to provide equal financial services to everyone worldwide. If only the wealthy can afford Gas fees, Ethereum loses its democratic meaning. Therefore, scaling solutions are not optional but essential.

How Rollups Work: Off-Chain Aggregation, On-Chain Verification

Simply put, the Ethereum mainnet (Layer 1) is the final arbiter of all transactions, responsible for ensuring security. But not all computations need to be performed on the mainnet. The core idea of Rollups is to move computation off-chain and report the results to the mainnet.

The specific process is as follows:

User transactions are executed on the Rollup chain (Layer 2). The Rollup chain is an independent blockchain with higher throughput and lower costs. After transaction execution, the Rollup aggregates and compresses many transactions into a summary data. This data is submitted back to the Ethereum mainnet via a smart contract. The mainnet only needs to verify the validity of this summary, not each individual transaction.

This mechanism yields significant effects: Ethereum’s TPS can increase from 15 to over 1000, while the Gas cost per transaction drops from around 45,000 GAS to about 300 GAS, reducing costs by approximately 150 times.

Optimistic Rollups vs Zero-Knowledge Rollups: Two Major Technical Approaches

However, Rollups have different implementation methods, and the Ethereum community has engaged in intense discussions about this. Currently, there are mainly two technical routes.

Optimistic Rollups: Speed and Trust Trade-off

The core of “Optimistic” is an optimistic assumption: it assumes that the submitted transaction data is correct by default and does not require active verification. If someone wants to cheat, other participants can submit a “fraud proof” to report it.

To prevent malicious behavior, the person submitting the batch of transactions must first deposit a security deposit (usually in ETH). If fraudulent transactions are detected, the deposit is forfeited. Reporters must also deposit a security deposit, and if their report is false, they will lose their deposit. This two-way deposit mechanism ensures network honesty.

Optimistic Rollups are already in practical use; Optimism and Arbitrum are the two most well-known protocols. Both operate on Ethereum and have achieved varying degrees of success.

However, Optimistic Rollups have a clear pain point: time cost. Before final confirmation of transactions, the system needs to leave enough time for others to submit fraud proofs. If someone reports fraud, further verification is required. The entire process can take days, sometimes even two weeks. This means users may have to wait a long time to see their transactions finally confirmed.

Zero-Knowledge Rollups: The Power of Mathematical Proofs

Zero-Knowledge Rollups (ZK-Rollups) adopt a completely different approach—using “Zero-Knowledge Proofs.”

A simple analogy: imagine you want to prove to a friend that you know a secret, but you don’t want to reveal what the secret is. Zero-Knowledge Proofs are such a tool—they can prove you possess certain information without revealing the content.

In the context of Rollups, Zero-Knowledge Proofs are used to verify the legality of a batch of transactions. Once the batch is submitted to the mainnet, it can be immediately validated mathematically without waiting for a fraud proof period. This solves the time issue of optimistic Rollups and further reduces the amount of data that needs to be uploaded to the mainnet.

From a technical design perspective, Zero-Knowledge Rollups are almost impossible to deceive—no one can forge a valid proof. Therefore, many members of the Ethereum community believe this is the ultimate solution to scalability issues.

But Zero-Knowledge Rollups also face challenges. The biggest problem is compatibility with EVM (Ethereum Virtual Machine). Existing applications on the Ethereum mainnet need to rewrite code to migrate to ZK-Rollups chains, which is a huge cost for developers.

Seeing this issue, projects like ZK-sync are developing EVM-compatible ZK-Rollups solutions. Once successful, ZK-Rollups will truly become a powerful tool to change Ethereum’s “rich man’s game” landscape. Currently, projects such as Loopring, Hermez, ZK tube, Aztec, Starkware, and others are exploring different applications of ZK-Rollups, each with its own features.

The Current and Future of the Rollups Ecosystem

When Rollups are fully deployed, what will happen to the Ethereum ecosystem?

Currently, there are hundreds of DeFi protocols on the Ethereum mainnet, with user numbers continuously increasing. Once Rollups mature, these protocols will operate in a low-cost, high-speed environment. This not only lowers the barrier for existing users but more importantly opens the door for new users—those who previously hesitated due to Gas fees can now easily use Ethereum DeFi.

Low costs and fast confirmation times will naturally attract new projects. Many applications that rely on “low cost, fast transactions”—which might have been impossible to realize on Ethereum before—will become feasible in the era of Rollups. This will bring in thousands of new users and developers.

It is worth noting that Ethereum may become the first blockchain to truly solve the “Blockchain Trilemma.” Ethereum’s development roadmap is already very clear: first complete the merge (unifying the consensus and execution layers), then upgrade with data sharding. The ultimate goal of these upgrades is to accelerate and enhance the performance of Rollups.

In other words, the entire future development of Ethereum revolves around Rollups. Rollups are not only a technological innovation but also a crucial step for Ethereum to realize its vision—making decentralized finance truly the choice for everyone worldwide, not just a privilege for the few.