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simon nungwa
simon nungwa

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🚀 Building a Scalable Startup with AWS: Secure Frontend Auth with Cognito + React

#aws #react #startup #opensource

How do you build a secure, scalable app as a solo founder without a massive budget? I’m doing it with AWS Cognito for KaziHub, a smart job board empowering African developers with verified tech jobs, scam detection, and skill-based matching.

In this post, I’ll walk you through how I implemented user authentication with Cognito + React + AWS Amplify — a stack perfect for lean startups looking to scale fast.

🧱 Why AWS Cognito?

Cognito is a powerhouse for startups like mine because:

  • ✅ Handles user sign-up, login, email verification, and password resets out of the box
  • ✅ Scales effortlessly, so I don’t worry about infrastructure as KaziHub grows
  • ✅ Integrates seamlessly with AWS services like Lambda, S3, and DynamoDB, which I’m using for job matching
  • ✅ Saves me from building a custom auth backend, keeping costs low and development fast

Cognito

AWS’s serverless tools are a game-changer for solo founders, letting me focus on KaziHub’s mission: connecting African developers with verified opportunities.

🔧 Setting Up Cognito

  1. Create a User Pool

    Go to AWS Console → Cognito → User Pools → Create new pool

    I enabled email as the sign-in method and applied strong password policies.

  2. Set up an App Client

    Created a client ID without a client secret (since the frontend is public).

  3. Configure the Hosted UI Domain

    This allows a seamless experience for verification, sign-up, and password recovery.

💻 Setting Up My React Frontend

Install AWS Amplify 

npm install aws-amplify
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Configure Amplify 

// src/awsConfig.js
export const awsConfig = {
  Auth: {
    region: "us-east-1",
    userPoolId: "us-east-1_XXXXXXX", // Replace with your User Pool ID (Based on how close it is to your location to reduce latency)
    userPoolWebClientId: "XXXXXXXXXXXXXX", // Replace with your App Client ID
  },
};
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// main.jsx
import { Amplify } from "aws-amplify";
import { awsConfig } from "./awsConfig";

Amplify.configure(awsConfig);
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🧑‍💻 Auth Flows

🔐 Sign Up 

import { Auth } from "aws-amplify";

const handleSignUp = async () => {
  await Auth.signUp({
    username: email,
    password,
    attributes: { email },
  });
};
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🔓 Login 

const handleLogin = async () => {
  await Auth.signIn(email, password);
};
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🔁 Recover Password 

await Auth.forgotPassword(email);
await Auth.forgotPasswordSubmit(email, code, newPassword);
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✅ Confirm Sign Up 

await Auth.confirmSignUp(email, code);
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🔒 Protecting Routes (Optional)

To protect authenticated-only pages (like posting jobs), I created a simple PrivateRoute component:

const PrivateRoute = ({ children }) => {
  const [user, setUser] = useState(null);

  useEffect(() => {
    Auth.currentAuthenticatedUser()
      .then(setUser)
      .catch(() => (window.location.href = "/login"));
  }, []);

  return user ? children : null;
};
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🧠 Lessons Learned

  • AWS documentation can feel dense. Setting up email flows and user pools took trial and error.
  • InvalidParameterException was my nemesis — usually caused by misconfigured attributes.
  • Once it’s set up, Cognito just works. It’s magical watching everything sync across the hosted UI and your frontend.

🛠 What’s Next

  • Build job posting + application logic using Lambda and DynamoDB
  • Add user roles for Job Seekers and Employers
  • Set up CI/CD pipeline with GitLab
  • Deploy via AWS Amplify Hosting or S3 + CloudFront

💬 Final Thoughts

AWS Cognito and Amplify have been game-changers for KaziHub. I’m building a secure, scalable platform for African developers — without having to manage infrastructure or auth complexity.

🚀 We’ve already onboarded 100+ users in beta, and thanks to Cognito, every sign-up, login, and password reset has been smooth.

Got questions or ideas? Ping me on X — happy to connect with fellow builders!

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