How Stable Built the World's Highest Yield Savings App with Smart Wallets

Stable is the world's highest yield savings app that lets everyday investors earn up to 10% per year on their savings with stablecoins. Unlike traditional savings accounts that compound interest once daily, Stable connects users directly to crypto money markets where deposits settle immediately and interest compounds every second.

To provide better financial services for their users, smart wallets were mission critical. Smart wallets enabled automatic rebalancing that moves user funds to the highest-yielding markets without requiring any user action, all secured with complete self-custody.

Built for both crypto newcomers who've never made a blockchain transaction and advanced investors seeking intuitive access to DeFi's largest lending markets, Stable has created a seamless savings experience that rivals traditional banking while delivering dramatically higher yields.

Self-Custody, Compliance, and Automation

As DeFi lending markets constantly shift, users miss out on optimal yields when they can't actively monitor and rebalance their positions. Traditional solutions force users to choose between convenience and control, but Stable wouldn’t compromise on either.

The Stable team faced three critical challenges:

• Eliminating user friction: Users needed their funds to automatically move to the highest-yielding markets without returning to the app or taking manual actions.

• Maintaining a non-custodial model: Any solution had to avoid regulatory gray areas, regardless of jurisdiction or enforcement climate.

• Simplifying complex operations: The interface needed to hide technical jargon while seamlessly executing multi-step DeFi strategies in the background.

"The largest barrier to mass adoption was enabling users to always earn the highest yield across curated lending markets without users having to come back to the app, entering a custodial gray-area, or dealing with technical jargon," the Stable team explained.

Before smart wallets, this trifecta was impossible to achieve. Users suffered from suboptimal yields and poor UX, constantly having to monitor markets and execute manual rebalancing transactions.

True Non-Custodial Automation with Smart Wallets

Stable needed to automate complex yield optimization strategies while maintaining complete non-custodial operations. This required solving two fundamental challenges: giving the app permission to move user funds automatically, and doing so without introducing any centralized control points.

The answer was session keys: temporary permissions that allow specific actions without exposing the user's main private key. But most session key implementations rely on off-chain infrastructure, creating potential custody concerns.

Alchemy Smart Wallets made this possible through ERC-6900, a standard we co-authored with the Ethereum Foundation, Circle, and Trust Wallet, that lets developers extend wallet functionality with plug-in modules. Stable implemented two key modules:

• The WebAuthN Module for secure biometric authentication using FaceID/passkeys through P256 signature verification using the secrp256r1 precompile

• The Session Key Module for completely onchain session keys that could automatically rebalance without relying on any third party.

Notably, passkey integration was particularly game-changing. Users' FaceID or fingerprint is their private key, backed up automatically through iCloud or their password manager. No seed phrases to write down, no private keys to lose, meaning crypto newcomers could onboard instantly.

The result? Users authenticate once with their biometrics, and the app can automatically move their funds to higher-yielding opportunities – all while maintaining complete self-custody and transparency.

Real Results: Higher Yields, Lower Costs, Better UX

Now, Stable can offer better experiences for their users at lower costs:

• 50% reduction in gas costs: Smart wallet optimizations mean Stable spends half as much on transactions, enabling them to put that capital to use elsewhere

• 1.5% higher average annual yields: Users earn an extra 1.5% per year simply because their funds automatically chase the best opportunities for them.

• One-click magic: What used to be "deposit USDC, then supply to lending market" became just "deposit". The app handles the rest instantly in the background.

• Crypto newcomers welcome: Users who'd never touched blockchain before can start earning DeFi yields without being exposed to blockchain jargon.

• Truly non-custodial automation: Stable can provide automated fund management that works completely onchain. No servers, no trusted parties, just smart wallets.

The team shared that "Alchemy's engineers have gone above and beyond – scheduling meetings within minutes, answering challenging technical questions about smart wallets and ERC-6900 smart contracts, developing custom SDK features uniquely for Stable, and being transparent about required upgrades. Easily 10/10!"

Join the Top DeFi Apps

As Stable prepares to roll out automatic rebalancing to all users and expand their offering of blue-chip lending opportunities, they're setting the standard for how DeFi savings products should work. Their users don't have to choose between security and convenience because smart wallets make it possible to have both.

We’re here to help more builders like you create the next generation of DeFi applications with smart wallets.

Start building today:

• Learn about Smart Wallets and try the demo

• Get in touch with our team or start building