Mesut Tekin
Verified Expert in Engineering
Software Developer
London, United Kingdom
Toptal member since April 13, 2020
Software architect and hands-on developer with 25+ years of experience designing and delivering large-scale, mission-critical platforms across fintech and regulated industries. Proven track record in building scalable, secure systems, integrating complex external networks, and leading greenfield products from concept to production. Experienced in cloud-native architectures, distributed systems, and SaaS platforms, with a strong focus on reliability, performance, and business outcomes.
Portfolio
Experience
- C# - 15 years
- Spring Boot - 8 years
- Docker - 8 years
- Java 8 - 8 years
- Kubernetes - 8 years
- Flask - 6 years
- Python 3 - 6 years
- Apache Kafka - 1 year
Preferred Environment
C#, Java, Python, DevOps, Architecture, Claude, Cursor AI, Retrieval-augmented Generation (RAG), Model Context Protocol (MCP), Lovable
The most amazing...
...thing was making a SaaS issuer-processor simulator from scratch, enabling realistic payment flows and used by several processors for certification and testing.
Work Experience
Lead Developer
Inspiration Tech
- Designed and implemented a SaaS application called the ITT Payment Simulator to emulate end-to-end payment authorisation and clearing flows, supporting card, fleet, and contactless environments.
- Provided hands-on consultancy to Tribe Payments and Clowd9 on card payment testing and performance, improving transaction reliability and network readiness.
- Automated test case generation and execution pipelines using Azure DevOps and Kubernetes.
- Built real-time monitoring dashboards in Grafana for transaction validation, reducing defect detection time by 40%.
- Developed dynamic UI components in React and C#, Java, and Node.js back ends to load contextual issuer environments.
AI Expert
BrainGym Limited
- Led the development, audit, and security hardening of an AI-powered facilitator platform designed for scalable workshop delivery and intelligent interaction.
- Architected a Modular Context Processing (MCP) server combined with a Retrieval-Augmented Generation (RAG) pipeline to enable efficient indexing, retrieval, and contextual understanding of uploaded materials.
- Performed comprehensive AI-generated code audits and penetration testing, identifying and remediating security vulnerabilities to ensure production-grade reliability.
- Designed a modular and white-label-ready architecture.
- Integrated external AI tools and APIs for enhanced facilitator workflows.
- Integrated Stripe payment system for magnetization.
Lead Developer
Thredd
- Involved the integration of Visa DPS and Mastercard Network Exchange, enabling issuer certification and live transaction processing across multiple card programs.
- Improved development and testing efficiency by introducing automated simulation tools that reduced dependency on external payment networks.
- Provided hands-on technical consultancy for authorisation improvements.
Lead Developer
XYZ Reality
- Developed microservices using Java, Spring, Python, React, and Go for a Building Information Modelling (BIM) and Augmented Reality system from scratch.
- Managed the DevOps environment (Jenkins, GCP, Kubernetes, Docker, CI/CD, Istio).
- Oversaw test automation development with Protractor and Selenium.
Senior Developer
Tesco Bank
- Developed microservices using Java, Kotlin, Spring, Python, and Flask for the digital wallet system.
- Automated tests using Cucumber, Gherkin, and Selenium.
- Managed and improved the DevOps environment (Jenkins, AWS, Azure Kubernetes, Helm, Tiller, Ansible, Docker, Apache Tomcat, Apigee, CI/CD), and migrated from AWS to Azure.
- Monitored and visualized logs using Splunk and AppDynamics.
Senior Developer
Santander UK
- Developed microservices using Java and Spring (Spring Boot, Data, cloud, Security) to integrate the Santander payment system with Mastercard.
- Automated tests using Cucumber, Gherkin, and Rest Assured.
- Built a message-based system using Rabbit MQ and Kafka.
Senior Developer
Ainfin, Ltd.
- Developed extensions to the Cyclos Core Banking platform using Spring and TDD and BDD methodologies.
- Improved the continues integration process with Jenkins.
- Reviewed and refactored the existing code with documentation.
Senior Developer
CampaignUp
- Developed a stand-alone Zendesk integration application from scratch.
- Added new functionalities to Zendesk Support by developing various Zendesk apps.
- Created end-to-end integration between the client application and Zendesk.
Lead Developer
Ziraat Tech and Ziraat Participation Bank
- Oversaw the technical analysis and architecture of projects.
- Developed a banking module for Ziraat Participation Bank using .NET technologies (C#, Windows Forms, WCF, Oracle).
- Managed the setting up of ADC (mobile, internet branch, ATM, call Center, to name a few).
Developer
Kuveyt Turk Bank
- Developed credit scoring for small business company with SAS and a retail company with Experian.
- Analyzed and developed a dashboard (MIS) including exposure, limit, follow-up, and collateral with using QlikView.
- Developed decision support systems for credit sectors (Rules Engine, C#, WCF, WPF, SQL Server).
Experience
AI Facilitator Platform (RAG and MCP Architecture with Security Audit & Scalable AI System)
https://braingymai.coI architected a Modular Context Processing (MCP) server combined with a Retrieval-Augmented Generation (RAG) pipeline to enable efficient indexing, retrieval, and contextual understanding of uploaded materials.
I also performed comprehensive AI-generated code audits and penetration testing, identifying and remediating security vulnerabilities to ensure production-grade reliability.
ITT Payment Simulator
https://itt.inspirationtech.co.uk/Digital Wallet Application
Card Payment System
Migration from AWS to Azure
Automated Loan Origination Approval
Setup of Bank
Banking Software Transformation
Education
Ph.D. in Business Management
Halic University - Istanbul, Turkey
Master's Degree in Computer Science
Bahcesehir University - Istanbul, Turkey
Master's Degree in Project Managememnt
Northeastern University - Boston, Massachusetts, USA
Bachelor's Degree in Computer Science
Marmara University - Istanbul, Turkey
Certifications
Project Management Professional
Project Management Institute
Microsoft Certified Professional
Microsoft
Skills
Libraries/APIs
REST APIs, Flask-RESTful, OpenAPI, React, OpenAI API, Node.js, Claude API, Pandas, Stripe API, jQuery, Windows Forms (WinForms), Apigee
Tools
Git, Azure Kubernetes Service (AKS), Amazon EKS, Google Kubernetes Engine (GKE), GitHub, Microsoft Access, Microsoft Excel, Claude Code, Claude, RabbitMQ, Cucumber, AppDynamics, Terraform, Jenkins, Gradle, Azure Application Gateway, Grafana, Apache Maven, Microsoft Copilot, Bitbucket, Pytest, JHipster, Visual Studio, MSTest, SPSS, Splunk, Tailwind Scheduling & Analytics
Languages
Java 8, Python 3, C#, Python, Java, SQL, HTML, JavaScript, C#.NET, GraphQL, TypeScript, Go, HTML5, Groovy, SAS, CSS
Frameworks
Spring Boot, Flask, .NET, .NET Core, Swagger, Selenium, Spock, Django, OAuth 2, Spring, Spring Security, Windows Presentation Foundation (WPF), Spring Batch, ASP.NET, Next.js, Tailwind CSS
Paradigms
REST, Microservices, Azure DevOps, Test-driven Development (TDD), DevOps, Microservices Architecture, Back-end Architecture, API Architecture, Model Context Protocol (MCP), Event-driven Architecture, Asynchronous Programming, Real-time Systems, RESTful Development, Building Information Modeling (BIM), Management
Platforms
Docker, Kubernetes, Azure, Amazon Web Services (AWS), Oracle, Google Cloud Platform (GCP), Linux, Zendesk, QlikView, Apache Kafka
Storage
PostgreSQL, Spring Data, MongoDB, MySQL, JSON, Amazon S3 (AWS S3), Redis, Database Integration, NoSQL, Microsoft SQL Server, SQL Server 2007
Industry Expertise
Banking & Finance, Cybersecurity
Other
Cloud, Architecture, Spring Cloud, CI/CD Pipelines, Startups, FastAPI, Software Architecture, Microsoft Azure, System Design, Back-end, APIs, Cursor AI, API Integration, Card Payments, Enterprise Architecture, Payment Processing, Digital Payments, QA Testing, Integration, Architecture, Card Payments, Code Review, Audits, Multi-tenant Architecture, Multi-tenant SaaS, Scalability, OAuth, API Testing, Enterprise Systems, Deployment, Online Banking, ChatGPT API, Web Development, System Architecture, Technical Leadership, Code Architecture, Google Cloud Build, Large Language Models (LLMs), Artificial Intelligence (AI), Finance, Fintech, Monday.com, Okta, OpenID Connect (OIDC), ISO 27001, Full-stack Development, Enterprise Architecture, Access Control, Data Modeling, Enterprise SaaS, Authentication, Authorization, Microsoft Entra, Credit Ratings, Full-stack, Generative Artificial Intelligence (GenAI), Retrieval-augmented Generation (RAG), AI Agents, Infrastructure, Shell Scripting, Back-end Admin Systems, Solution Architecture, Gemini, Payments, AI Automation, Lovable, AI Integration, WebSockets, Edge Functions, Data, Security, Boot, Cyclos, Windows Communication Foundation (WCF), AI Content Creation, OpenTelemetry, .NET Core 8, Supabase, Supabase Auth, Vite, Tailwind UI
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