Understanding Light Clients - A simple breakdown with an Artisan Marketplace analogy

DA is a core principle of blockchains. Not an afterthought, but a must-have.

One of the major innovations that optimized DA layers like Avail have implemented is “data availability light clients”.

Let’s take a look at LCs through a simple analogy of an Artisan Marketplace :point_right:

Light clients are a necessary component in any blockchain as it allows users to interact with a chain without storing the entire chain data. Traditionally, they cannot operate independently, and rely on full nodes to provide the truth.

Imagine you’re in a vibrant marketplace :moyai: with a traditional blockchain architecture. You’ve got the diligent artisans (validator nodes), the inspectors and distributors (full nodes), and the end consumers (light clients).

The artisans, craft blocks like potters at the wheel, they collect materials (txs) from the surrounding environment (mempool), mold them into a coherent shape (execute txs), and create a new product (generate a candidate block). After this, they’re ready to hand off their work✨ The discerning inspectors and distributors (full nodes), step into the scene. They get the new product (candidate block) from the validator nodes and meticulously examine it for any flaws. If approved, they distribute the product across the marketplace. If not, they reject it.

The consumers - LCs - are interested in the final products (blocks) but lack the ability to inspect every detail. They trust the inspectors to provide them with the best products, requesting headers and tx details as needed. They trust that what they receive is of good quality.

Within this bustling marketplace though, there is a threat of counterfeit goods (double spend). Imagine a scenario where a malicious manufacturer (validator) tries to smuggle in counterfeit goods. When a validator node attempts to smuggle counterfeit goods, full nodes spot the fakes instantly.

The inspectors (full nodes) have the ability to reject these goods, creating a new market where only authentic products are allowed—a fork, if you will. However, the everyday customers (light clients) who are not able to verify the goods are left at the mercy of these manufacturers and inspectors. LCs trust the merchant’s (full node’s) word implicitly, without the resources to verify the authenticity of the goods.

We see the precarious position the light clients are in. They are vulnerable and are at the mercy of the full node’s honesty and integrity. Hence we require a more robust solution.

Enter Avail :rocket:

Avail is laser-focused on the task of data availability, which allows us to rethink how each network participant of the blockchain can be improved, and optimized for the task.
There’s a better way for blockchains to be built.

Avail’s solution addresses the limitations of traditional LCs by empowering them with the ability to perform data availability sampling.

We will go into how Avail solves the problem for the “marketplace” with what it does.

Data Availability Sampling (or DAS) is a new superpower for light clients to achieve security equivalent to full nodes.
DAS is the process Avail’s light clients use to request small, random pieces of each block. Confidence builds progressively with each successful sample.

Once verified, the data is deemed to be available, which allows confident interaction with the rest of the modular blockchain stack.

For this to work, we redefine all of the network peers in Avail. Let’s understand by diving back into the Artisan Marketplace analogy.

We find a revolutionary shift in the roles of the marketplace. The artisans, inspector-distributors, and consumers undergo a transformation, bringing forth an efficient, robust, and more decentralized blockchain architecture.:rocket:

In Avail’s marketplace, the validator nodes still play the artisans, but their role is slightly different.
They no longer mold the clay (executing txs) but rather, they prepare the raw materials (packaging txs) and construct the shape of the product (creating candidate blocks).

While the full nodes are still present in Avail’s marketplace, their role has diminished. :bust_in_silhouette: They are no longer main inspectors or distributors anymore, they act more like a reserve or a backup, ensuring the high redundancy of the products.:truck: They are no longer the gatekeepers of the marketplace, and the majority of the marketplace’s operations can proceed without them. :gear:

What’s revolutionary in Avail’s marketplace is the role of the consumers, the light clients. :eyes:

Imagine you give each consumer a special magnifying glass that verifies the integrity of the goods they receive.

Now the light clients are empowered to sample tiny pieces of the product (DAS), comparing it to unique signatures (KZG commits) provided by the artisans.

They are no longer dependent on the word of the inspector-distributors (full nodes); they can verify the authenticity of the products themselves. In case the artisans (validator nodes) decide to withhold information about the products (data unavailability), the consumers, now equipped with their magical magnifying glasses, can identify the missing data on their own.

Now here’s the crazy part - a feature only on Avail - These empowered LCs also contribute to maintaining the marketplace’s liveliness. As they sample the products, they keep a record in a shared ledger (Distributed Hash Table - DHT), ensuring data availability in the market. In a sense, they collectively create a ‘backup’ of all the recent transactions, ensuring that the marketplace stays alive even if some or all artisans (validator nodes) and inspector-distributors (full nodes) go offline.

Imagine millions of LCs in a P2P network keeping a collective record of their tiny samples creating a cohesive backup of the data until the network is back online.
Avail is the only DA layer that can sample from its light client P2P network instead of relying on full nodes.


This exclusive feature sets Avail apart from all current and planned Data Availability solutions, providing a robust fail-safe mechanism and enhancing the resilience of Avail’s Data Availability network.

With Avail’s innovative approach, we give them power back to the consumers by providing with the ability to maintain security equivalent to full nodes, and yet with a light client that can run on your browser, phone, or even a smartwatch (not kidding!)

By eliminating the need to trust the inspector-distributors (full nodes), Avail’s marketplace allows for truly decentralized and efficient operations, paving the way for a new era in blockchain technology.

This analogy was first explained in one of our earlier 3-part blog posts, and goes into much more detail: Limitations of Traditional Blockchain Light Client
Light Clients (Part 2): How Avail light clients overcome the challenges of monolithic chains
Light Clients (Part 3): Trust Issues? Avail light clients have you covered


2-3 years ago, I didn’t think that light clients could have a function other than SPV and that they could be developed so much, things are completely different when the whole focus is on data availability. I am very curious about the blockchains that will be created by combining the best of each layer for modular blockchain. :sunglasses: