E. is available for hire
Hire E.E. Deniz Toktay
Verified Expert in Engineering
Software Developer
Istanbul, Turkey
Toptal member since February 9, 2022
Bio
Deniz is a Java architect, technical team leader, and software developer who has worked on complex projects for multinational companies like Amadeus, Turkcell, Vodafone, Tav Technologies, and others. Having worked in various industries, such as foreign exchange, insurance, travel, and communication, Deniz feels most comfortable solving challenging problems, liaising with multiple teams, mentoring professionals, and solving conflicts in different teams.
Portfolio
Allwyn Entertainment
Java 21, Spring Boot, Docker, PostgreSQL, Apache Kafka, Git, Kubernetes, Redis
Pfizer - Smart Factory
Java, Spring, Back-end, Microservices, Amazon Web Services (AWS), SQL...
Pfizer - Smart Factory
Java, Spring, Back-end, Microservices, Amazon Web Services (AWS), Networking...
Experience
- Java - 8 years
- Databases - 8 years
- Spring Boot - 7 years
- Scrum - 6 years
- Git - 6 years
- Python 3 - 4 years
- Software Architecture - 3 years
- Kotlin - 2 years
Work Experience
Senior Staff Engineer
2026 - 2026
Allwyn Entertainment
- Modernized existing lottery systems utilized across multiple countries; designed and developed new games tailored for diverse markets, including the Czech Republic.
- Contributed to Agile development sprints, delivering new modules based on Jira tickets with high TDD standards and robust integration testing.
- Ensured refactored code satisfied all requirements, successfully passed validation testing, and seamlessly passed off ownership to maintenance teams.
Technologies: Java 21, Spring Boot, Docker, PostgreSQL, Apache Kafka, Git, Kubernetes, Redis
Java Back-end Developer
2025 - 2025
Pfizer - Smart Factory
- Architected and developed a multi-site labeling solution leveraging EKS-based microservices to bridge site-specific data sources (SAP, SQL/NoSQL databases) with local printing infrastructure.
- Developed and maintained a multi-site labeling platform across geographically dispersed locations, leveraging Jira for Agile task management and cross-functional coordination.
- Successfully deployed the solution to packaging departments across 3 active sites, with 4 additional locations prepared for the upcoming rollout.
- Mitigated global latency issues caused by geographically distributed data stores by designing and implementing a Redis-based datagrid, enabling low-latency, multi-site data fetching for centralized microservices.
Technologies: Java, Spring, Back-end, Microservices, Amazon Web Services (AWS), SQL, Terraform, DevOps, Networking, APIs, Windows PowerShell, Git, Ansible, REST, Docker, Kubernetes, Azure, Infrastructure as Code (IaC)
Java Back-end Developer
2024 - 2024
Pfizer - Smart Factory
- Integrated an AI-powered documentation system and built an AWS-based alerting tool to detect production line sensor anomalies, leveraging AI to recommend actionable solutions.
- Developed brand-new back-end modules, services, and integrations for the Batch Buddy production line alarm tool, while integrating a documentation service with a chatbot to enhance search capabilities.
- Monitored and validated the successful deployment of the new module on the production line of one of the highest-volume plants.
Technologies: Java, Spring, Back-end, Microservices, Amazon Web Services (AWS), Networking, APIs, DevOps, Terraform, SQL, Windows PowerShell, Infrastructure as Code (IaC), REST, Docker, Kubernetes, Azure, Git, Ansible, AWS Lambda, Python 3, Historian Server, Snowflake, Microsoft SQL Server, AI Model Integration
Java Back-end Developer
2023 - 2023
Pfizer - Smart Factory
- Engineered a centralized documentation portal connecting multi-site production facilities and R&D centers globally.
- Engineered new modules and custom integrations while resolving critical bugs, utilizing Jira for task tracking and Agile execution.
- Architected a multi-site, multi-language portal to centralize global internal documentation retrieval, featuring robust role-based authorization controls.
Technologies: Back-end, Java, Spring, Microservices, Amazon Web Services (AWS), Networking, SQL, Terraform, DevOps, APIs, Docker, Git, Kubernetes, REST, Windows PowerShell, Ansible, Infrastructure as Code (IaC), Azure, AWS Lambda, Python 3, Spring Microservice, Microsoft SQL Server
Spring Boot 3.0 Developer
2023 - 2023
Ziiware Inc
- Developed security modules to use Firebase tokens for stateless role-based access control (RBAC) for Spring Boot 3.0 and Hilla (Vaadin Confluence).
- Used JetBrains Space as code repository and tracing tool.
- Created web security modules for a newly started project to use further developments.
Technologies: Spring Boot, Java, Java 17, Firebase, Cloud Firestore, Role-based Access Control (RBAC), Vaadin, Spring Security, React, JavaScript, TypeScript 3, Frameworks, APIs, REST, REST APIs
Senior Python and Java Developer
2022 - 2022
Envoy Technology Ltd
- Examined and redesigned the project architecture. Found project defects and security defects. Created reports for the current project and future improvements.
- Used AWS Lambda to provide a serverless architecture. Used Miro and other tools to provide architectural design and existing defect flows.
- Redesigned the startup's architecture and roadmap to provide a new pathway to its internal developers, which they had tried to do before but couldn't tackle the development and architectural challenges.
Technologies: Python, Java, Node.js, AWS Lambda, Amazon Web Services (AWS), Architecture, Back-end, Back-end Performance, Back-end Development, APIs
Senior Freelance Developer
2022 - 2022
Elemy
- Developed applications to create scheduling between providers and clients.
- Tracked and fixed bugs using Jira as a reporting tool.
- Created Datadog dashboards and monitors for the application's health metrics and alarms.
Technologies: Kotlin, PostgreSQL, Hasura, GraphQL, JOOQ, MJML, Nylas API, Docker, Jira, Git, Datadog, Amazon Web Services (AWS), Okta, JUnit, Docker Compose, Spring Boot, SendGrid, Thymeleaf, Testcontainers, Scheduling, Task Scheduling, Amazon Simple Queue Service (SQS), GitHub, Java 11, APIs
Technical Team Lead
2021 - 2022
Vodafone Group
- Developed and led back-end modules for IoT projects, including registration, billing, and more.
- Integrated Camunda business process management with the WSO2 authentication system.
- Defined proof of concept for Camunda business process management's dynamic generation of user tasks.
- Developed the complex Camunda business process model and notation (BPMN) processes and related actions.
- Managed a development team and supported other teams as a technical lead.
Technologies: Spring Boot, PostgreSQL, Apache Kafka, MongoDB, Git, Jira, Scrum, Java, Databases, JUnit, Docker, Testcontainers, Docker Compose, SonarQube, Spring, Spring Integration, Spring Batch, WebFlux, Hibernate, Spring Data JPA, Apache Maven, Web Services, SQL, Back-end Development, Back-end Performance, OAuth, OAuth 2, Secure Web Development, Amazon Web Services (AWS), GraphQL, REST, REST APIs, GitHub, Java EE 8, Spring Data MongoDB, Back-end, Back-end Architecture, APIs, Java EE (Jakarta EE)
Freelance Developer
2021 - 2021
Web Help Turkey
- Converted the existing .NET legacy codes to .NET Core using NuGet.
- Reviewed and refactored .NET codes to improve Genesys Intelligent Interaction Server communication.
- Improved the existing development and team development experience. Provided stability to the legacy codebase.
Technologies: .NET, Microsoft SQL Server, Genesys, NuGet, .NET Core, Back-end Development, Back-end Performance
Freelance Developer
2020 - 2021
Web Help Turkey
- Developed a custom alarm manager to control the scheduled database task completion, emit rest calls to manage scheduled service status, and send notifications via a phone call or email using a custom rule engine.
- Developed monitoring dashboards and generated reports emailed to managerial users.
- Completed more than 200 database tasks, emitted more than 50 different service rest calls daily, and generated notifications according to the rules.
Technologies: Java, Microsoft SQL Server, Spring Boot, Windows Server, JUnit, Docker Compose, Docker, SonarQube, Spring Data, Spring Data JPA, Hibernate, Apache Maven, SQL, Back-end Development, Secure Web Development, CI/CD Pipelines, PrimeFaces, REST, REST APIs, Job Schedulers, Scheduling, Java 11
Software Architect Consultant
2020 - 2021
Anadolu Sigorta
- Developed the architectural design concept for the biggest Turkish insurance company's digital channels using microservices and cloud technologies.
- Built abstraction and infrastructure libraries to use in microservices.
- Created third-party connections, such as other internal or external platforms and libraries.
- Developed common authentication and authorization modules using JSON Web Token technologies.
- Headed three projects simultaneously to complete their revamp using common architectural principles and standard libraries.
- Developed the architecture and libraries still used by three mobile and one web project.
Technologies: Java, Oracle, Spring Boot, Jenkins, Spring Cloud, Apache Kafka, Graylog, Hazelcast, Git, Jira, Scrum, DevOps, Databases, Software Architecture, JUnit, Spring, Spring Batch, React Native, React, RxJava 2, Hibernate, WebFlux, Apache Maven, Web Services, SQL, Back-end Development, Back-end Performance, Security, OAuth, OAuth 2, Web Security, Secure Web Development, Java Security, CI/CD Pipelines, Architecture, Microservices Architecture, Domain-driven Design (DDD), Message Queues, REST, REST APIs, Python 3, Java 11, MongoDB, Back-end, Back-end Architecture, Back-end Admin Systems, Mobile Back-end, APIs, Java EE (Jakarta EE)
Senior Software Engineering Consultant
2018 - 2020
TAV IT Services
- Participated in developing the new Istanbul airport's ground service allocation platform as a technical lead and software architect.
- Built an abstraction library for microservices, such as security, data source connection, messaging, and more.
- Developed messaging and other orchestration modules.
- Integrated platform health tools, such as Grafana and Prometheus, into all developed modules.
- Used Python to develop custom deployment tools compatible with the Bamboo platform and distributed them to remote restricted Windows servers.
- Developed integration modules to obtain real-time data from aircraft and ground handling units, such as flight data rosters.
- Contributed to developing the sorting algorithm to match tasks and resources using predefined rules.
- Tracked and fixed bugs using Jira as a reporting tool.
- Activated the platform before the start of the pandemic. It handled more than 1,500 flights per day using real-time data from aircraft.
Technologies: Java, Microsoft SQL Server, Python 3, Git, Spring Boot, Prometheus, RabbitMQ, Jira, Scrum, DevOps, Databases, Software Architecture, JUnit, Apache Kafka, Elastic, SonarQube, Spring, Spring Integration, Spring Batch, Keycloak, REST APIs, Hibernate, Apache Maven, Web Services, SQL, Back-end Development, Back-end Performance, Security, Back-end, OAuth, OAuth 2, Web Security, Secure Web Development, Java Security, CI/CD Pipelines, Microservices Architecture, Spring Microservice, Domain-driven Design (DDD), Message Queues, OpenShift, REST, Scheduling, Job Schedulers, Task Scheduling, GraphQL, Java 11, MongoDB
Senior Software Engineering Consultant
2018 - 2018
Turkcell
- Developed the payment integration for the BiP messaging platform and end-to-end testing suite.
- Created proof of concept for the existing BiP platform and their business services.
- Developed basic image-creating tools to send daily notifications to subscribed users.
Technologies: Oracle, MongoDB, Apache Kafka, Docker, Python 3, Git, Scrum, Java, Spring Boot, Databases, JUnit, Docker Compose, Spring, Spring Batch, Hibernate, RxJava 2, Akka, Apache Tomcat, Gradle, Web Services, SQL, Back-end Development, Back-end Performance, Secure Web Development, Message Queues, Kubernetes, Helm, APIs, REST, REST APIs, SOAP, Java EE 8, Java EE (Jakarta EE)
Master Software Development Engineer
2014 - 2018
Amadeus
- Participated in developing and headed the airline loyalty platforms, client contact center platform, mail parsing and assignment platform, and reporting tools as a technical lead.
- Tracked and fixed bugs using Jira as a reporting tool. Became the first point of contact for clients with security issues as a white hat developer.
- Prepared and conducted secure development lifecycle and defensive programming training sessions within the company, which significantly reduced security-oriented bugs.
- Released the new platforms enabling Amadeus to sell them to major airlines in the Middle East, Eastern European, and Central American regions.
Technologies: Secure Web Development, JSF, Jakarta Server Pages (JSP), Oracle, PrimeFaces, Git, Scrum, Java, Spring Boot, Databases, Oracle PL/SQL, SonarQube, JUnit, Spring, Spring Integration, Spring Batch, EclipseLink, Hibernate, Apache Tomcat, JBoss AS, WebSphere, Apache Maven, Web Services, SQL, Back-end Development, Back-end Performance, Back-end, Security, OAuth, OAuth 2, Web Security, Java Security, REST, PL/SQL, SQL Stored Procedures, APIs, REST APIs, SOAP, Java EE (Jakarta EE)
Senior Software Engineering Consultant
2012 - 2013
Destek Menkul Değerler
- Developed real-time news feed, recommendation, and price servers for FX users.
- Created a web push comet server for HTML4 standard using Python and Twisted framework.
- Developed JavaScript to get web push records in HTML4 web pages.
Technologies: Python 2, Twisted, MySQL, PyQt 4, JavaScript, REST APIs, Apache HTTP Server, Web Services Description Language (WSDL), Web Services, SQL, Back-end Development, REST
Project History
New Generation Insurance App Juno
Juno is a mobile application that allows users to buy different types of insurance. I worked on it as a technical architect and back-end engineer. The application was awarded a silver prize in the Turkish Customer Experience Awards.
Asenta Agent Portal | Mobile App
I worked as a technical architect and back-end developer on the revamp project of the Asenta agent portal and insurance API platform. More than 3,000 agents use the Asenta platform daily to handle all insurance operations. It uses the same back-end servers as the Ofisim Cepte mobile app. A custom rule-based authorization service has been implemented to cover flexible authorization changes based on user type, platform, IP definitions, etc.
Sigortam Cepte Insurance | Mobile Application
The Sigortam Cepte mobile application enables Anadolu Sigorta's clients to handle all their insurance-related operations, such as renewing and claiming premiums, reporting damage, buying health insurance, and more. I worked as a technical architect and technical lead on this application.
Ground Handling Suite
https://tavtechnologies.aero/en-EN/products/airport-operations/pages/ground-handling-suite-products-servicesI contributed to the project's architecture and development phases by creating proof of concept and drafting architectural designs. Also, I developed a project skeleton and abstraction tools for the microservices, third-party integration, and a real-time data consumption and orchestration module. A custom Python-based distributed deployment module for Windows servers was developed.
Elemy Main Suite
Elemy is a VC-funded startup that provides home care for children who have autism. The main functionality is to match children with a suitable child psychologist and create their appointments automatically.
I participated in the design and development of matching and scheduling back-end modules. New modules and several integrations, such as AWS, Nylas, Twilo, and so on, were developed using Kotlin and Spring Boot.
I participated in the design and development of matching and scheduling back-end modules. New modules and several integrations, such as AWS, Nylas, Twilo, and so on, were developed using Kotlin and Spring Boot.
Education
2005 - 2010
Bachelor's Degree in Computer Science
Macquarie University - Sydney, Australia
Certifications
APRIL 2023 - PRESENT
AI for Trading
Udacity
MARCH 2021 - PRESENT
Deep Learning
Udacity
Skills
Libraries/APIs
REST APIs, Java Security, React, RxJava 2, JOOQ, Nylas API, PyQt 4, Node.js, Natural Language Toolkit (NLTK)
Tools
RabbitMQ, Docker Compose, Apache Maven, Git, Jenkins, SonarQube, Apache Tomcat, Jira, SendGrid, GitHub, NuGet, Graylog, OneSignal, Grafana, Elastic, Keycloak, Apache HTTP Server, Gradle, Helm, Amazon Simple Queue Service (SQS), Terraform, Ansible
Languages
Java, Python, Web Services Description Language (WSDL), SQL, Kotlin, Python 3, Python 2, JavaScript, GraphQL, Dart, Java 11, Java EE 8, Scala, TypeScript 3, Snowflake, Java 21
Frameworks
Spring Boot, JSON Web Tokens (JWT), JUnit, Spring, Spring Batch, Hibernate, OAuth 2, PrimeFaces, Jakarta Server Pages (JSP), Spring Microservice, Flutter, Spring Integration, WebFlux, JSF, .NET, .NET Core, React Native, Akka, Twisted, MJML, Thymeleaf, Vaadin, Spring Security, Windows PowerShell
Paradigms
Microservices Architecture, REST, Back-end Architecture, Scrum, DevOps, Role-based Access Control (RBAC), Microservices
Platforms
Oracle, Docker, Apache Kafka, Amazon Web Services (AWS), Windows Server, WebSphere, Kubernetes, OpenShift, AWS Lambda, JVM, Blockchain, Firebase, Java EE (Jakarta EE), Azure
Storage
Oracle PL/SQL, Spring Data JPA, Spring Data, MySQL, PL/SQL, SQL Stored Procedures, Databases, Hazelcast, PostgreSQL, Hasura, Microsoft SQL Server, Couchbase, Spring Data Elasticsearch, JBoss AS, Datadog, Spring Data MongoDB, MongoDB, Cloud Firestore, Redis
Other
Software Architecture, Distributed Systems, Spring Cloud, LDAP, Testcontainers, EclipseLink, Web Services, Back-end Development, Back-end Performance, OAuth, Secure Web Development, Web Security, Architecture, Domain-driven Design (DDD), Message Queues, Scheduling, Back-end, Back-end Admin Systems, Mobile Back-end, Security, Prometheus, CI/CD Pipelines, Deep Learning, Genesys, AS400, Okta, Job Schedulers, Task Scheduling, Java 17, Frameworks, APIs, SOAP, Natural Language Processing (NLP), Trading, Stock Market, Stock Exchange, Stock Price Analysis, Bonds, Fintech, Networking, Infrastructure as Code (IaC), Historian Server, AI Model Integration
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