Building a Yield Optimizer on Celo: A Hands-On Guide to Decentralized Finance (DeFi) Strategies

Building a Yield Optimizer on Celo: A Hands-On Guide to Decentralized Finance (DeFi) Strategies
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Decentralized Finance (DeFi) is a revolution in the financial sector, leveraging blockchain technology to democratize access to financial services. With DeFi, traditional banking services such as lending, borrowing, trading, and yield generation are now accessible to anyone globally. However, the landscape is vast, and there are often complexities and risks involved. In this tutorial, we are aiming to mitigate some of these complexities, particularly focusing on yield optimization.


Before starting this tutorial, you should have:

  • A strong understanding of JavaScript and Solidity programming languages.
  • A basic understanding of blockchain and the Celo ecosystem.
  • Node.js and npm installed on your system.
  • A Celo Wallet and some testnet tokens for deployment on the testnet.
  • Basic familiarity with Hardhat and ContractKit.


For this tutorial, you will need:

  • A code editor like Visual Studio Code.
  • Node.js and npm, which can be installed from the Node.js website.
  • Hardhat, which can be installed via npm with npm install --save-dev hardhat.
  • Celo’s ContractKit, which can be installed with npm install @celo/contractkit.
  • A Celo wallet. If you don’t have one, you can create it at the Celo website.

I. Introduction to Yield Optimization

Yield optimization refers to strategies aiming to maximize return on capital by automatically leveraging various DeFi protocols. These strategies usually involve smart contracts that automatically move funds between different liquidity pools to earn the best possible yield.

II. Understanding the Celo Ecosystem

Celo is a mobile-first blockchain platform aimed at increasing cryptocurrency adoption among mobile users. Using Celo, developers can create, deploy, and scale decentralized applications more easily than other blockchain platforms. The platform has its native stablecoin, Celo Dollar (cUSD), which we’ll use in this tutorial.

III. Building the Yield Optimizer

Setting Up the Development Environment

First, install Hardhat and create a new Hardhat project:

npm install --save-dev hardhat
npx hardhat

To interact with the Celo network, we will use ContractKit, a library provided by Celo. Install it using npm: npm install @celo/contractkit.

Designing the Yield Optimizer Architecture

The Yield Optimizer contract needs to manage user deposits, find and interact with high-yielding farms, and implement auto-compounding strategies. Design this architecture carefully, considering user security and gas efficiency.

Programming Smart Contracts in Solidity

Let’s start writing the yield optimizer contract. The contract will use the ERC20 interface for interacting with tokens. We’ll specify the address of the token we’ll be using (in our case, cUSD). The deposit function transfers tokens from the user to the contract, and the withdraw function does the opposite. We will also introduce an IFarm interface that our contract can use to interact with different farms. The deposit function now stakes tokens in the farm, and the withdraw function withdraws from the farm.

We also add a new function harvestAndReinvest that harvests rewards from the farm and re-stakes them for compounding.

// SPDX-License-Identifier: MIT
pragma solidity ^0.6.6;
import "@celo/contractkit/contracts/IERC20.sol";

interface IFarm {
    function stake(uint amount) external;
    function withdraw(uint amount) external;
    function getReward() external;

contract YieldOptimizer {
    IERC20 celoToken;
    IFarm currentFarm;

    constructor(address _celoToken, address _farm) public {
        celoToken = IERC20(_celoToken);
        currentFarm = IFarm(_farm);

    function deposit(uint amount) public {

, address(this), amount);
        // Stake in farm
        celoToken.approve(address(currentFarm), amount);

    function withdraw(uint amount) public {
        // Withdraw from farm
        celoToken.transfer(msg.sender, amount);

    function harvestAndReinvest() public {
        // Harvest rewards from farm
        // Assume rewards are in celoToken
        uint balance = celoToken.balanceOf(address(this));
        // Re-stake rewards
        celoToken.approve(address(currentFarm), balance);

As stated, this code is a simple demonstration and lacks error handling, security checks, and optimizations necessary for production code. You’ll need to enhance it with additional features, such as support for multiple farms, tracking of individual user balances, and so on.

Deploying and Interacting with the Smart Contract using Hardhat

Once the contract is ready, use Hardhat’s deployment scripts to deploy the contract on the Celo network.

The following code snippet demonstrates how to interact with your deployed contract using Hardhat and ethers.js:

const { ethers } = require("hardhat");

async function main() {
  const contractAddress = '...'; // Replace with your deployed contract address
  const YieldOptimizer = await ethers.getContractFactory("YieldOptimizer");
  const yieldOptimizer = YieldOptimizer.attach(contractAddress);

  // Call deposit function
  const depositAmount = ethers.utils.parseUnits("1", 18);
  await yieldOptimizer.deposit(depositAmount);

  .then(() => process.exit(0))
  .catch((error) => {

Now, let’s add the deployment and interaction script for the smart contract.

Deploying the Yield Optimizer Smart Contract

We’re going to use a Hardhat deployment script to deploy our smart contract on the Celo network. Here’s an example of how you could write the script:

// scripts/deploy.js

async function main() {
    const [deployer] = await ethers.getSigners();

        "Deploying contracts with the account:",
        await deployer.getAddress()

    console.log("Account balance:", (await deployer.getBalance()).toString());

    const Token = await ethers.getContractFactory("YieldOptimizer");
    const celoTokenAddress = '...'; // Replace with cUSD contract address
    const farmAddress = '...'; // Replace with Farm contract address
    const yieldOptimizer = await Token.deploy(celoTokenAddress, farmAddress);

    console.log("YieldOptimizer address:", yieldOptimizer.address);

    .then(() => process.exit(0))
    .catch((error) => {

You can run this script with npx hardhat run scripts/deploy.js --network alfajores. Make sure to replace '...' with the appropriate cUSD and Farm contract addresses.

IV. Navigating High-Yielding Farms

In this tutorial, we have hardcoded the farm in the contract for simplicity. However, in a more complete yield optimizer, the contract should be able to switch between different farms depending on which one offers the highest yield. This could be achieved by implementing a governance mechanism that allows the contract to change the current farm, or through a more complex, on-chain algorithm.

V. Implementing Auto-Compounding

The harvestAndReinvest function in our contract is a simple example of an auto-compounding function. When called, it collects any rewards the contract has earned from the farm, then reinvests them by staking them back into the farm. This compounds the user’s return over time. However, to make it work in a real-world scenario, you would need a way to call this function regularly. This could be done by users, an external service, or a decentralized autonomous organization (DAO).

VI. Managing Risk in Yield Optimization

Keep in mind that yield farming and yield optimization involve substantial risk. Things like smart contract bugs, hacks, sudden changes in return rates, or even admin key vulnerabilities can lead to a total loss of funds. Therefore, always follow best practices in contract development, conduct thorough testing, and possibly even acquire security audits.

What’s Next?

After completing this tutorial, you can:

  • Explore other yield optimization strategies.
  • Implement more advanced features into your yield optimizer.
  • Learn about and implement additional security measures.
  • Deploy your yield optimizer on the Celo mainnet.
  • Experiment with other DeFi protocols on the Celo network.


Here are some references to help you understand the tutorial better:

Remember, this tutorial is meant as a starting point. Building a real-world yield optimizer involves solving many more challenges and requires a thorough understanding of both Solidity programming and DeFi protocol.

About the Author

Elijah Sorinola

Web3 technical writer with a passion for communicating complex technical concepts in a clear and concise manner. Let’s connect on LinkedIn to discuss your content needs.


Here are some references to help you understand the tutorial better:


I’m guessing you mean to use the New Request tag? right @Elijah007


Congratulations on your proposal being chosen as a standout this week at Celo Academy! As you prepare your tutorial, please ensure you follow our guidelines found here: Celo Sage Guidelines and Best Practices. Thank you for helping improve the experience of the developers learning at Celo Academy.


@Celo_Academy I need a reviewer for this, please.


Hi @danielogbuti have you gotten the chance to go through this? Let me know what you think.


Hi @danielogbuti I just fixed that. Kindly take another look and let me know what you think…


Looks good :+1: