Data Availability Layers in Modular Blockchains Explained

Most people think blockchains scale by making blocks bigger or faster. That’s not how it works anymore. The real breakthrough isn’t speed-it’s data availability. If you can’t prove that all transaction data was published, no one can verify the chain. And that’s where data availability layers (DALs) come in. They’re not flashy. They don’t process smart contracts. They don’t even run apps. But without them, rollups like zkSync and Arbitrum wouldn’t work at all.

What Is a Data Availability Layer?

A data availability layer is a dedicated system that stores raw transaction data and proves it’s out there-publicly and permanently. Think of it like a digital warehouse for blockchain receipts. Every time a rollup processes 10,000 transactions, it doesn’t post them all to Ethereum’s main chain. Instead, it dumps the raw data onto a DAL, like Celestia or EigenDA. Then, it posts a tiny cryptographic proof saying, “All this data exists and hasn’t been tampered with.”

This solves the biggest bottleneck in scaling: full nodes used to need to download and store every single byte of every block. On Ethereum, that’s over 1.2 terabytes of data as of late 2023. No consumer laptop can handle that. So most users run light clients-tiny programs that only check a few pieces of data. But if the data isn’t actually there, those light clients get fooled. That’s the data availability problem. DALs fix it with math, not bigger hard drives.

How Data Availability Sampling Works

The magic behind DALs is called data availability sampling (DAS). Instead of downloading an entire block, your light client randomly grabs 30 to 40 small chunks of data from it. If all those chunks are available, you can be 99.9% sure the whole block is there. You don’t need to see everything. You just need to see enough to trust it.

This works because of erasure coding. Before data gets published, it’s split into 2x more pieces than needed. So even if half the pieces go missing, you can still rebuild the whole thing. Celestia uses Reed-Solomon coding for this. Ethereum uses KZG polynomial commitments-a more advanced math trick that lets nodes prove data exists without revealing it.

The result? A light client on Celestia only needs 1-2 GB of storage. On Ethereum today, you need over a terabyte. That’s the difference between running a node on your laptop versus needing a data center.

On-Chain vs. Off-Chain Data Availability

There are two main ways to build a DAL: on-chain and off-chain.

On-chain means storing data directly on the main blockchain. Ethereum is doing this with proto-danksharding (EIP-4844), launching in Q2 2024. It adds special data containers called “blobs” to each block. These blobs hold rollup data but cost far less than regular transaction data. Ethereum’s current on-chain DAL can handle 15-45 transactions per second. After the upgrade, it could hit 100,000 per second. But it’s still limited by Ethereum’s consensus and security rules. Gas fees for rollups will drop by about 90%, according to Ethereum Foundation research from January 2023.

Off-chain means using a separate network just for data. Celestia is the pioneer here. It doesn’t run smart contracts. It doesn’t settle payments. It just stores and proves data. In Q3 2023, Celestia was processing 1.25 MB per block, with 300-500 transactions per second and 10-15 second finality. Its testnet achieved 1 MB per second throughput. And transaction costs? Around $0.0001 per transaction. That’s 10,000 times cheaper than Ethereum’s current gas fees.

EigenDA, built on Ethereum’s EigenLayer, uses restaking to secure its data layer. In August 2023, it hit 100,000 transactions per second in testnet. That’s faster than Solana-but without Solana’s outages. Celestia had 99.98% uptime in Q3 2023. Solana had seven major outages in 2022.

Who’s Leading the Pack?

Three names dominate the DAL space right now: Celestia, Ethereum, and EigenDA.

Celestia is the purest form of a DAL. It’s designed for one thing: data availability. It’s built on the Cosmos SDK, so it’s not EVM-compatible. That means developers need to learn new tools. As of November 2023, only 15 rollups were live on Celestia. But it’s growing fast. Coinbase invested $50 million in it in September 2023. Binance Labs put $100 million into modular blockchain infrastructure in October 2023.

Ethereum’s path is different. It’s not replacing its chain-it’s upgrading it. Proto-danksharding is a step toward full sharding. It keeps data on-chain, so security stays tied to Ethereum’s proof-of-stake validators. But it’s complex. The upgrade was delayed from Q4 2023 to Q2 2024. Ethereum’s GitHub has over 120 open issues just on KZG commitment integration. Still, it’s the most trusted option because it inherits Ethereum’s security.

EigenDA is the wildcard. It’s not a new blockchain. It’s a data availability service running on top of Ethereum. It uses restaked ETH for security, meaning validators who stake on Ethereum can also secure EigenDA. That gives it Ethereum-level security without the throughput limits. It’s already being tested by enterprise teams. One architect on the Ethereum Research forum said its documentation was “excellent,” but mainnet delays hurt their timeline.

Then there’s Avail, from Polygon. It’s a three-layer system: data availability, cross-chain interoperability, and multi-token security. It’s designed for enterprise use. Polygon announced its Avail-based DAL for enterprise clients in October 2023.

Why This Matters for Developers

If you’re building a blockchain app, your choice of DAL affects everything: cost, speed, security, and who can use your app.

Using Ethereum’s on-chain DAL means your users pay Ethereum gas fees-just lower ones. Your app is secure, but you’re still tied to Ethereum’s congestion. You can’t easily move to another chain.

Using Celestia means your app runs on a new ecosystem. You’ll need to use Cosmos-based tooling. Only 12% of blockchain devs are fluent in Cosmos SDK, according to a November 2023 survey by Electric Capital. But your users pay pennies. And you’re not competing with other apps for block space.

EigenDA gives you Ethereum security without the cost. But it’s newer. Fewer tools. Less community support. Only 22 reviews on GitHub compared to Celestia’s 37.

Most developers need 3-4 weeks to get up to speed on DALs, according to Consensys Academy’s November 2023 training data. The learning curve isn’t steep-it’s just different. You’re not coding smart contracts anymore. You’re thinking about data, proofs, and sampling.

Challenges and Risks

It’s not all smooth sailing. Even with all the progress, there are big problems.

First, tooling is immature. Developers on Reddit reported an 87% cost drop after switching to Celestia-but said “tooling maturity” was a nightmare. GitHub issues for Celestia’s sampling code number 47. Ethereum’s danksharding has 123.

Second, interoperability is a mess. There’s no standard for how DALs talk to each other. A rollup on Celestia can’t easily move data to a rollup on EigenDA. The Interchain Foundation is funding a $5 million project to fix this, but it’s still early.

Third, security assumptions are tricky. Ethereum researcher Dankrad Feist warned in January 2023 that data availability sampling requires careful parameter tuning. If you sample too few pieces, you’re vulnerable. Too many, and you lose efficiency. The University of Illinois study in July 2022 confirmed the math works-but said real-world networks might be messier than theory predicts.

And then there’s regulation. The EU’s MiCA framework, effective December 2024, will require all blockchain transactions to have verifiable data availability. That could force companies to adopt DALs-even if they don’t want to.

What’s Next?

The future is modular. By 2026, Gartner predicts 70% of new blockchain apps will use dedicated data availability layers. Right now, it’s 15%. That’s a 4.7x jump in under three years.

Celestia’s upcoming “Arbital” upgrade in Q1 2024 will add validity proofs-meaning it won’t just store data, but also prove the transactions inside it are correct. That’s a huge leap. It’s starting to blur the line between data availability and execution.

Ethereum’s roadmap is still the most watched. If proto-danksharding works as planned, rollup costs could drop to a fraction of a cent. That could unlock millions of new users.

The market is reacting. Investment in DALs jumped from $25 million in 2021 to $420 million in 2022, according to Messari. The whole DAL market is projected to hit $8.7 billion by 2027.

This isn’t a trend. It’s a rewrite of how blockchains work. The days of monolithic chains trying to do everything are ending. The future belongs to chains that specialize: one layer for execution, one for settlement, one for data. And the data layer? It’s the foundation. Without it, nothing else holds up.