Decentralized Applications: Wallet Integration, Ethers/Web3 Patterns, and Backend Architecture
Learn how user-facing blockchain applications combine frontend wallet flows, smart contracts, indexing, and backend services.
Inside this chapter
- What a dApp Actually Includes
- Wallet Connection and Transaction Flow
- Why Backends Still Matter
- Production Architecture Example
Series navigation
Study the chapters in order for the smoothest path from beginner blockchain concepts to advanced architecture and production practices. Use the navigation at the bottom of each page to move chapter by chapter.
What a dApp Actually Includes
A decentralized application is rarely just a smart contract. Most real products include a frontend, wallet integration, one or more contracts, backend APIs, off-chain storage, indexing services, and monitoring systems. Some logic lives on-chain for trust and transparency, while other logic stays off-chain for performance, privacy, or cost reasons.
Wallet Connection and Transaction Flow
import { ethers } from "ethers";
const provider = new ethers.BrowserProvider(window.ethereum);
const signer = await provider.getSigner();
const contract = new ethers.Contract(contractAddress, abi, signer);
await contract.increment();This common pattern connects a browser wallet, acquires a signer, creates a contract instance, and sends a state-changing transaction.
Why Backends Still Matter
Many beginners assume Web3 removes the need for backends. In practice, backends still help with analytics, search, notifications, rate limiting, private business logic, fiat integrations, indexing, fraud detection, and aggregating blockchain data into fast APIs. The difference is that some critical state or settlement logic is anchored on-chain.
Production Architecture Example
An NFT marketplace might use a React frontend, wallet integration for signing, contracts for listing and purchase logic, IPFS or object storage for media, an indexing service for events, and a backend for user profiles, email, moderation, and marketplace analytics. Mature blockchain products are hybrid systems, not purely on-chain systems.