Contact person: iOS/Backend Developer Needed to Fix Sign Up & Sign In Flow (SwiftUI + Twilio + JWT + PostgreSQL/Railway)

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Location: Silver Spring, United States

Budget: Recommended by industry experts

Time to start: As soon as possible

Project description:
"Description:
I’m building a payment app (CetePay) in SwiftUI with a backend hosted on Railway using Flask (Python) + PostgreSQL. The app’s sign-up/sign-in process has been the biggest roadblock, and I need an experienced developer to step in and fully fix/establish a working, production-ready authentication flow.
Right now:
I’m using Twilio Verify for phone number OTP authentication.
The backend is built with Flask and returns tokens using JWT.
User data is stored in a PostgreSQL database on Railway.
The frontend is iOS (SwiftUI).
The issues I’m facing:
Response mismatch between backend and frontend (snake_case vs camelCase fields).
iOS app expects certain fields (accessToken, refreshToken, isNew, profileComplete) but backend isn’t returning them consistently.
JWT secret setup is inconsistent (sometimes empty/invalid).
Navigation flow on iOS fails after OTP because it can’t parse/validate the response.
No reliable persistence of tokens in Keychain for session management.
Deliverables:
Fix and finalize sign-up & sign-in flow
OTP verification with Twilio → Backend validates → iOS app receives proper structured JSON response.
Return the correct fields (accessToken, refreshToken, expiresIn, isNew, profileComplete, user).
JWT & Token Handling
Generate and validate JWT properly with a secure secret.
Ensure refresh token flow works.
Store tokens securely on iOS (Keychain).
Backend Alignment
Standardize Flask response format to what the iOS app expects.
Connect cleanly to PostgreSQL for user account management.
iOS Integration
Ensure SwiftUI app properly parses backend response.
Correctly routes new users to registration, existing users to dashboard.
Persist logged-in state.
Requirements:
Strong experience with SwiftUI, Flask/Python, JWT, PostgreSQL, and Railway (or similar hosting).
Experience with Twilio Verify API.
Proven ability to debug and fix authentication flows end-to-end.
Knowledge of secure storage on iOS (Keychain).
Goal:
By the end of the project, I want a fully working, production-ready authentication system where:
A new user enters their phone → receives OTP via Twilio → verifies → creates account → logged in.
An existing user logs in seamlessly.
Tokens are issued, validated, and refreshed without errors.
State is persisted securely and the user always lands in the correct screen (registration vs dashboard)." (client-provided description)