You will get I will audit and secure your Node.js backend and payment integrations
Project details
Secure Your Backend & Fix Payment Vulnerabilities Before They Cost You.
Worried about insecure payment flows or Google Play Store rejections? I am a Senior Backend Developer specializing in high-security financial integrations and API hardening.
Having successfully audited and implemented systems for DC Bank (MD5 Protocols) and Razorpay apps, I know exactly where the "leaks" happen in Node.js and FastAPI backends.
Why Choose This Project:
Audit-First Approach: I perform a deep-dive security audit to find vulnerabilities you didn't know existed.
Play Store Compliance: I ensure your subscription flows strictly follow store policies to avoid rejections.
Hardened Logic: I move critical business logic (like admin approvals) to the server-side, making it impossible to bypass via frontend.
Financial Expertise: Specialized in signature verification, secret key management, and accurate balance calculations.
Tech Stack:
Backend: Node.js (Express), FastAPI.
Databases: MongoDB, PostgreSQL.
Security: JWT, RBAC, MD5/SHA Signature Verification.
Let’s perform a professional audit and harden your backend logic today.
Worried about insecure payment flows or Google Play Store rejections? I am a Senior Backend Developer specializing in high-security financial integrations and API hardening.
Having successfully audited and implemented systems for DC Bank (MD5 Protocols) and Razorpay apps, I know exactly where the "leaks" happen in Node.js and FastAPI backends.
Why Choose This Project:
Audit-First Approach: I perform a deep-dive security audit to find vulnerabilities you didn't know existed.
Play Store Compliance: I ensure your subscription flows strictly follow store policies to avoid rejections.
Hardened Logic: I move critical business logic (like admin approvals) to the server-side, making it impossible to bypass via frontend.
Financial Expertise: Specialized in signature verification, secret key management, and accurate balance calculations.
Tech Stack:
Backend: Node.js (Express), FastAPI.
Databases: MongoDB, PostgreSQL.
Security: JWT, RBAC, MD5/SHA Signature Verification.
Let’s perform a professional audit and harden your backend logic today.
Programming Languages
JavaScript, TypeScriptCoding Expertise
Performance Optimization, Security, DesignWhat's included
| Service Tiers |
Starter
$50
|
Standard
$120
|
Advanced
$250
|
|---|---|---|---|
| Delivery Time | 2 days | 4 days | 7 days |
Number of Revisions | 1 | 2 | Unlimited |
Design Customization | - | - | - |
Content Upload | - | - | - |
Responsive Design | - | - | - |
Source Code |
Frequently asked questions
5 reviews
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SD
Saveen D.
Apr 23, 2026
Backend Payment Integration
Professional and skilled, will work with again!
AS
Ayesha S.
Mar 28, 2026
Python Developer for Screen Monitoring Tool
Excellent developer and great experience working together. He was very responsive, patient, and committed to fixing all issues until everything worked exactly as requested.
AT
Ashish T.
Feb 25, 2026
Senior Backend / Full-Stack Developer for Live Creator Earnings App (FastAPI, MongoDB)
Ozenc is technically capable and delivered substantial backend and frontend modifications within the milestone. However, after deployment, the system experienced production instability requiring rollback and mediation through Upwork. Clients should ensure clear scope alignment, staging validation, and infrastructure readiness before production deployment.
SD
Saveen D.
Feb 4, 2026
Backend Payment Integration (DC Bank)
Great experience working with Ozenc. Communication was clear and timely, the work was delivered as expected, and they followed instructions carefully. Professional, reliable, and easy to work with. I’d be happy to work together again in the future.
AD
Ash D.
Jan 29, 2026
Razorpay Audit & Google Play Store Readiness (Node.js App – NO Rebuild)
Ozenc helped stabilize and secure a live production application under time pressure and evolving requirements. He was transparent in his communication, identified backend risks, and implemented controlled testing mechanisms to validate critical flows without impacting real users or funds.
The project involved live deployments, branch management, and security-sensitive logic, and Ozenc handled these responsibly while explaining technical trade-offs clearly. I appreciate his patience during coordination and his commitment to finishing the task properly.
I would recommend him for backend security reviews, audits, and stabilization tasks, especially where production safety matters.
The project involved live deployments, branch management, and security-sensitive logic, and Ozenc handled these responsibly while explaining technical trade-offs clearly. I appreciate his patience during coordination and his commitment to finishing the task properly.
I would recommend him for backend security reviews, audits, and stabilization tasks, especially where production safety matters.
About Ozenc
Senior Python Backend Architect | AI & LLM Integration | n8n Automatio
80%
Job Success
Antakya, Turkey - 1:04 pm local time
I specialize in building scalable, production-ready backends using Python (FastAPI, Flask) and integrating cutting-edge AI/LLM models to automate complex workflows. Whether you need a robust API architecture or a custom AI agent, I deliver clean, Dockerized, and well-documented code.
Core Expertise:
• Backend: Python, FastAPI, PostgreSQL, MongoDB, Redis.
• AI & Data: OpenAI API, LangChain, Pandas, NumPy, TA-Lib (Trading Bots).
• Automation: n8n, Zapier, Custom Python Scripts.
• DevOps: Docker, AWS/DigitalOcean, CI/CD.
While my primary focus is Backend & AI, my proficiency in Node.js and React allows me to bridge the gap between complex logic and seamless user interfaces, ensuring a holistic architectural approach.
I don't just write code; I build systems that scale.
Steps for completing your project
After purchasing the project, send requirements so Ozenc can start the project.
Delivery time starts when Ozenc receives requirements from you.
Ozenc works on your project following the steps below.
Revisions may occur after the delivery date.
Initial Code Review & Documentation Analysis
I will examine your source code architecture, environment variables, and existing payment integration logic to identify immediate vulnerabilities.
Security Testing & Logic Hardening
I will perform manual and automated tests on your API endpoints, verify Razorpay/Payment signatures, and ensure all admin-level actions are strictly server-side controlled.