Mintlayer Back to Basics #7

Many public blockchains are powerful and secure, but they are not very fast. When lots of people try to use the same network at the same time, transactions can slow down and fees can spike. If we want blockchains to support everyday payments, trading, and real world finance, we need a way to handle more activity without giving up security. ZK Rollups are one of the clearest answers to that problem.

What is a ZK Rollup?

A ZK Rollup is a separate system that helps a blockchain process more transactions without forcing the base chain to do all the work. The easiest way to picture it is like a business that does not submit every single line item to the bank one by one.

Instead, imagine a merchant processes thousands of small purchases in a day, then sends the bank one final statement that summarizes what happened, along with a receipt that proves the totals add up correctly. The bank does not need every detail of every purchase to trust the final number, it just needs a reliable proof that the summary is correct.

That is what a rollup does for a blockchain. It collects many transactions, processes them together, and then posts a compact summary back to the base chain, along with a cryptographic proof that the updates follow the rules.

The word “rollup” comes from this idea of rolling many transactions into one verified update.

What does “zero knowledge” mean?

The “ZK” in ZK Rollup stands for “zero knowledge.” This refers to a type of cryptography that lets someone prove something is true without revealing all the underlying details.

A simple example is age verification. A venue only needs to know that you are over 18, not your exact birthday or address. Zero knowledge proofs work in a similar way. They let the network verify that a batch of transactions is valid without needing to expose every detail in the open.

For users, this can help in two ways. Proofs are small, which saves space and reduces costs, and they can support better privacy because correctness can be verified without showing everything.

How ZK Rollups work in practice

A ZK rollup works by letting most activity happen on a separate layer, then using the main chain only as the final judge. Users send transactions to the rollup (often through an app or wallet), and a rollup operator collects many of these transactions, orders them, and executes them inside the rollup environment. The operator then computes what everyone’s updated balances should be after that batch is processed.

Instead of posting every transaction to the main chain, the rollup posts a compact update that represents the new “snapshot” of the rollup’s ledger, along with a validity proof. This proof is a cryptographic certificate that says the batch followed the rules, meaning the math checks out and no one’s balance was changed incorrectly.

The main chain has a smart contract that verifies this proof. If the proof is valid, the contract accepts the batch and records the new snapshot as the official state of the rollup. Importantly, the base chain does not need to re-run every transaction to trust the result, it only needs to verify the proof.

This is why ZK rollups can feel faster and cheaper for users. Many transactions share the cost of a single on chain verification step, while the base chain still enforces correctness for every update.

Why ZK Rollups matter

ZK Rollups try to balance three important goals at the same time: scale, cost, and security.

They increase scale because most of the heavy processing happens outside the base chain, and many transactions are bundled into a single update. They reduce costs because the fee for posting that update is shared across the whole batch rather than paid individually. They keep security high because the base chain still verifies the proof and finalizes the result, so the rollup inherits the security of the underlying blockchain.

This is why many people see ZK Rollups as a strong long term approach to scaling.

Where ZK Rollups are useful

ZK Rollups can support almost any use case that needs high speed and low fees.

They make payments more practical by reducing congestion and cost. They help DeFi apps run with smoother execution and faster user experience while still settling back to a secure base layer. They also enable large scale NFT and gaming activity without overwhelming the main network.

In short, they help blockchain applications behave more like modern web apps in speed and cost, while keeping the transparency and resilience that make blockchains valuable.

ZK Thunder Network and Mintlayer

At Mintlayer, ZK Rollup technology is part of the longer term vision for Bitcoin aligned finance. ZK Thunder Network is Mintlayer’s Layer 3 built on top of the Mintlayer network. It uses zero knowledge technology to offer one second block times and full EVM compatibility, so developers can run smart contract applications in a high speed environment that still connects back to Mintlayer and, through Mintlayer, to Bitcoin.

If you want to see how it works in practice, you can explore the ZK Thunder public testnet.

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