How to Build Cross-Chain Applications

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Did you become a blockchain developer so you could be in a walled garden, following a strict set of limitations and instructions, only interacting with others on your particular blockchain?

I’m guessing not. The whole promise of decentralized development is not having your work tied to a single proprietary system. Your choice of platform shouldn’t be confining; it should be liberating.

Cross-chain applications are key to a truly decentralized, multiple-choice future. Building cross-chain applications is a strategic necessity for developers to reach wider audiences, offer better user experience, and get access to greater liquidity.

Here’s a quick guide to cross-chain development, including how we’re making Avalanche cross-chain friendly.

Why Cross-Chain Matters for the Future of Blockchain Development

The blockchain field has been divided into multiple isolated ecosystems. Each one has its own tokens, communities, guidelines and protocols. This kind of structure helped spark innovation in the early days, but now it’s clear how limiting a divided landscape can be.

Projects end up locked to the blockchain they’re built on, unable to bring in users from other chains or offer services that span multiple platforms. Without new users, new ideas, and the freedom for developers on different platforms to work together, innovation quickly slides into stagnation.

Cross-chain applications empower developers to use their platform of choice for development, without having to lock out the majority of their potential user base. These applications reward users with the ability to move assets and use services freely between blockchains, without sacrificing security or decentralization.

The alternative to a cross-chain future is an increasingly divided blockchain development space, with each platform supporting a tiny fraction of developers and users. That’s the polar opposite of the future most blockchain developers had in mind when they started.

The Challenges of Cross-Chain Development

It’s clear that cross-chain is a better way to build on the blockchain. But there are still limitations and trade-offs that need to be addressed. Layer 2 solutions can help boost scalability, but they also can fragment communities, limit liquidity and lead to volatility in gas fees.

Cross-chain bridges are a historical solution, but their structure can introduce security vulnerabilities. These vulnerabilities have already led to high-profile hacks and significant losses.

Ultimately, the major issue to solve is reducing trade-offs: Developers shouldn’t have to choose between speed, security and level of decentralization. 

Cross-chain development requires a platform that promotes secure, scalable, and fully interoperable applications.

Best Practices for Cross-Chain Application Development

It takes planning and skill to build a cross-chain application that delivers on interoperability without taking a performance or usability hit. That said, if you’re familiar with web3 development, you can create a cross-chain app, especially on a platform designed to support this kind of flexibility. Keep these best practices in mind:

Define Your Use Case

Not every application needs to have cross-chain functionality. Ask yourself:

• Do users of this app need access to other ecosystems?
• Will this app be transferring assets between chains?
• Does this app need a boost in liquidity?

If so, you likely have a use case for a cross-chain app. For example, a decentralized finance app could use cross-chain to access a broader liquidity pool. An NFT marketplace could use cross-chain capabilities to reach more potential collectors. 

It’s important to see where interoperability will add genuine value and make that the core of your application.

Start with Security

Vulnerabilities in cross-chain bridges are a common target for attackers. It’s important to use decentralized, established and vetted cross-chain protocols. Avoid shortcuts when implementing interchain bridges or messaging.

It’s also important to test your app rigorously and under various conditions, and to regularly conduct security audits.

If you’re building on Avalanche, take advantage of the Avalanche’s native Interchain Messaging (ICM) protocol. It’s designed with security as a top priority, and does not rely on any trusted third party or external decentralized message relayer. Instead, it leverages Avalanche’s P-chain to ensure the messages are transferred in a secured way. 

ICM allows sending any type of message, so one action in one chain can trigger any type of action on another, bringing true interoperability whenever is needed. On top of ICM, the Avalanche Interchain Token Transfer (ICTT) protocol enables the transfer of assets between L1s. It locks assets on the source chain and mints remote representations of them on the destination chain in a decentralized, transparent and verifiable way.

Understand the Finality Role in Interoperable Systems

When building interoperable systems between independent chains, it is important to understand that each chain only knows about events happening on another chain when a message is delivered. 

If an action happens on chain A that triggers a message to execute some action in chain B, it's important that chain B waits until the chain A transaction gets final before executing its own action. Otherwise, if the transaction in chain A gets reverted and chain B already executed its own action, this could lead to an undesirable state. 

Since Avalanche’s transactions get finalized immediately after confirmation, building interoperable applications on Avalanche results in convenient and fast interoperability operations.

Embrace the Developer Community

Cross-chain ecosystems require collaboration and community building. Use open-source tools and keep your development process transparent; this makes it easier to get community feedback and improve your build over time.

Community interaction across chains builds trust and can help strengthen the interoperability of your application. Working with developers on other chains can help you refine cross-chain functions that are applicable to platforms you’re not familiar with.

Optimize User Experience 

When you’re working in cross-chain environments, user experience is more complex. At the same time, providing a consistent positive user experience is crucial. A streamlined interface can hide the complex cross-chain transactions that make your app work, letting users focus on interacting with your services instead of fretting about what asset is on which chain.

Aim for clear and concise transaction information, low-latency interactions, and simplified token management.

Avalanche9000 Is Built for Cross-Chain Development

Avalanche was designed to make cross-chain development easier. The network has a robust tool set to help manage everything from liquidity to smart contract functionality.

Avalanche9000 has a unique architecture: Instead of solely using L2s operating on a shared L1, each app on Avalanche has the option to create its own L1. This “network of L1s” communicates with the each other chain through Interchain Messaging, providing a seamless, responsive and scalable development environment. Developers can also use their EVM of choice for their builds.

It's clear that a segregated, isolated walled garden approach is not the preferred future for blockchain. Cross-chain development offers a better experience for developers, users, and platforms alike.

Check out the Avalanche9000 launch page to learn more about the development of Avalanche L1s.

Start Building on Avalanche

Avalanche is making it easier and more cost-effective to build on blockchain. Avalanche9000, our latest upgrade, lowers the cost of entry and simplifies the development process. Check out our Developer Hub to get started.