Understanding the Architecture of a Web 3.0 Application (DApp)

Web 3.0 differs fundamentally from Web 2.0 by removing centralized intermediaries. This article uses the Ethereum ecosystem as an example to illustrate the architecture of a Web 3.0 application, progressing from Web 2.0 concepts to a full DApp stack.

(1) Web 3.0 Application (DApp) Architecture vs. Web 2.0

Using a simple blog platform (Medium) as a case study, a typical Web 2.0 stack consists of:

Database : stores user profiles, posts, tags, comments, likes, etc.

Backend code (Node.js, Java, Python, …): implements business logic for actions such as user registration, posting, commenting.

Frontend code (JavaScript, HTML, CSS): defines the UI and handles user interactions.

All three layers are hosted on centralized servers and accessed via a web browser.

(2) What Makes Web 3.0 Different?

In a Web 3.0 DApp there is no centralized database or server. Instead, a decentralized state machine (the blockchain) maintains all application state. Smart contracts, deployed on the blockchain, replace traditional backend services. The frontend remains largely unchanged, but it now communicates with smart contracts through blockchain nodes.

The architecture looks like this:

(3) Blockchain Basics

Ethereum is described as a “world computer”: a globally accessible, deterministic state machine maintained by a peer‑to‑peer network. Data written to Ethereum is immutable – it can never be updated.

Smart contracts are programs (written in Solidity, Vyper, etc.) that define the logic for state transitions. They are compiled to EVM bytecode, which the Ethereum Virtual Machine (EVM) executes.

(4) Front‑end ↔️ Smart Contract Communication

Front‑ends interact with the blockchain via a provider – either a self‑run node or a third‑party service such as Infura, Alchemy, or Quicknode. Providers implement the JSON‑RPC specification, allowing the front‑end to read blockchain state. To write state, a transaction must be signed with the user's private key.

Metamask acts as both a provider and a signer: it stores the user's private key in the browser and signs transactions on demand.

(5) Off‑chain Decentralized Storage

Storing all data on‑chain is expensive. Solutions like IPFS or Swarm provide peer‑to‑peer storage, while Filecoin adds an incentive layer. Front‑end assets can be hosted on these networks to avoid centralized points of failure.

(6) Data Querying

Two main approaches are used:

Smart‑contract events (e.g., via Web3.js) – real‑time but limited.

The Graph – an off‑chain indexing service that exposes a GraphQL API for efficient queries.

(7) Scaling (Layer 2)

Ethereum’s high gas fees and limited throughput motivate Layer 2 solutions:

Polygon – a side‑chain that batches transactions and periodically commits to Ethereum.

Optimistic Rollups and zkRollups – roll up many transactions off‑chain and submit succinct proofs to the main chain.

These approaches keep security on the main chain while moving most computation off‑chain, resulting in lower fees and faster confirmations.

(8) Developer Tooling

Frameworks such as Hardhat, Truffle, and Remix simplify smart‑contract development, testing, and deployment. Hardhat provides a local network, a rich plugin ecosystem, and console‑style debugging.

Conclusion

The article summarizes the end‑to‑end stack of a Web 3.0 DApp: blockchain as the immutable backend, smart contracts for business logic, decentralized storage for assets, providers for node access, and modern tooling to streamline development.