Full-Stack Developer for GPT Platform

Job Title: Full-Stack Developer – Customization & API Setup for GPT (Get-Paid-To) Rewards Platform   Job Description: We are launching Clock-It, a specialised Get-Paid-To (GPT) platform targeting the South African market. The platform rewards users with virtual points for completing micro-tasks, which they can then redeem exclusively for digital, branded betting vouchers (e.g., Hollywoodbets, Betway, Easybet).   We are procuring a pre-made GPT script framework (Laravel backend with a React Native or Flutter mobile app) and need a seasoned Full-Stack Developer with explicit, proven experience in the reward-app domain to handle deployment, deep structural customization, and advanced third-party integrations.   Key Responsibilities & Deliverables: 1. Script Deployment & UI Customization: Deploy our purchased script onto AWS or a high-concurrency VPS. Extensively skin the web/mobile interface to match our custom premium brand identity. 2. Third-Party API & Offerwall Integration: Seamlessly connect external ad networks, market research survey providers (Cint, CPX Research), and micro-poll/task offerwalls. 3. Advanced Micro-Task Habit Loops: Build out a seamless reward framework including a Daily Check-In streak bonus, a randomized Daily Lucky Wheel, and continuous Rewarded Video Ad loops. 4. Voucher Redemption Engine: Build a custom workflow that translates virtual points (e.g., 2,000 points = R20) into live digital vouchers, including a two-way referral engine that pays instant bonuses and a lifetime 10% recurring commission on friend tasks. 5. Ironclad Platform Security (Crucial): ◦ Implement bulletproof cryptographic postback signature verification (MD5/SHA256 handshakes) to prevent fake task completions. ◦ Integrate automated API layers to block VPNs, proxies, emulator software, and device duplication. Required Experience: • Explicit portfolio pieces demonstrating previous work on GPT platforms, reward portals, or offerwall-heavy mobile apps. • Strong mastery of PHP/Laravel, Node.js, and mobile cross-platform frameworks (React Native or Flutter). • Deep understanding of asynchronous callbacks, webhooks, and database optimization for tracking millions of concurrent micro-transactions. Project Type: Hybrid (Fixed-price milestones preferred for initial build; hourly contract available for ongoing optimization, security patches, and scaling). Budget: Competitive / Based on experience. Please state your experience with GPT platforms in your proposal.   To Apply, Please Answer: 1. Can you share links to or screenshots of a GPT/Reward platform you have previously developed or integrated? 2. How do you technically prevent postback/callback fraud (exploiters injecting points into their accounts)? 3. What framework (Laravel + React Native vs. others) do you recommend for this type of high-concurrency platform and why?