Deniz Mersinlioğlu, Developer in Istanbul, Turkey
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Deniz Mersinlioğlu

Verified Expert  in Engineering

Mobile Developer

Istanbul, Turkey
Toptal Member Since
August 27, 2021

Deniz is a tech lead and developer with 6+ years of experience working with startups and fast-paced companies. He specializes in full-stack development with React and Node.js, as well as mobile development for iOS and React Native. He has a strong history of creating MVPs and improving existing products, resulting in robust and scalable applications. Deniz has a solid background in project management, technical architecture, and leadership, which allows him to lead productive development teams.


React, JavaScript, TypeScript, Node.js, Express.js, Firebase Cloud Functions...
JavaScript, TypeScript, Node.js, Firebase Cloud Functions, Firebase...
React Native, React, Redux, Redux Thunk, Material UI, Framer X, Swagger...




Preferred Environment

Xcode, Visual Studio Code (VS Code), MacOS, Slack, Zoom

The most amazing...

...thing I've developed are React web and iOS native products for a Cisco-acquired B2B-SaaS startup.

Work Experience

Tech Lead and Senior Full-stack Developer

2023 - PRESENT
  • Led a team of six developers in developing and implementing an AI content creation platform using technologies such as React, Firebase Cloud Functions, Firestore, Stripe, Node.js, and TypeScript.
  • Utilized Firebase and Firestore to efficiently store and retrieve data and implemented Firebase Cloud Functions to automate back-end tasks such as data validation and manipulation.
  • Created a highly collaborative team from the ground up by fostering open communication, encouraging teamwork, and providing support and guidance.
  • Integrated Stripe for secure payment processing, enabling the platform to handle financial transactions such as subscriptions and one-time payments.
  • Created and assigned tasks to the developers, ensuring that work was properly distributed and prioritized.
  • Used Node.js and TypeScript to build a scalable and maintainable server-side architecture, ensuring efficient communication between the front end and back end through the use of APIs and network protocols.
  • Leveraged React to create a user-friendly and intuitive interface, enhancing the user experience using design patterns, state management, and performance optimization techniques.
  • Reviewed pull requests over GitHub to ensure code quality and adherence to project standards.
Technologies: React, JavaScript, TypeScript, Node.js, Express.js, Firebase Cloud Functions, Firebase, Firebase Hosting, Firebase Realtime Database, Cloud Firestore, Cloud Run, Next.js, Firebase Authentication, Redux Thunk, Redux, OpenAI, GitHub, Stripe, Stripe API, Stripe Payments, Technical Architecture, Technical Leadership, Leadership, Front-end

Senior Full-stack and React Native Developer

2023 - 2023
  • Designed and implemented a scalable and secure architecture for the React Native app, utilizing Node.js for the server-side logic and Firebase for the database and authentication.
  • Launched the React Native app, played a key role in full-stack development, and delivered high-quality products.
  • Built REST APIs using Node.js and cloud functions for data manipulation and user authentication, enabling efficient communication between the app's front end and back end.
  • Developed the app's front end using React and the react-native library, resulting in a seamless and intuitive user experience.
  • Implemented real-time data synchronization with the Firebase database using React and the React Native Firebase library, allowing for timely and accurate data updates.
  • Utilized Firebase's authentication services to implement secure user login and registration flows.
  • Incorporated several third-party libraries, such as React Navigation, to enhance the functionality and usability of the app.
Technologies: JavaScript, TypeScript, Node.js, Firebase Cloud Functions, Firebase, Firebase Realtime Database, Firebase Cloud Messaging (FCM), iOS, Android, Express.js, Technical Architecture, Technical Leadership, Leadership

Senior React Native Developer

2022 - 2022
  • Developed a minimum viable product (MVP) for a startup using React Native, resulting in a fully functional mobile app.
  • Designed and implemented a performant and highly responsive user interface by carefully planning the application's architecture and optimizing the layout and components for mobile devices.
  • Worked closely with the business team to ensure that the app met their requirements and provided valuable feedback on the designs made in Framer.
  • Improved the efficiency of API and client communication by reviewing the endpoints shared via Swagger and providing suggestions for optimization.
  • Ensured the app was ready for launch by conducting thorough testing and debugging.
Technologies: React Native, React, Redux, Redux Thunk, Material UI, Framer X, Swagger, Minimum Viable Product (MVP), Mobile Development, Mobile App Development, Cross-platform, Cross-platform App Development

Senior React Native Developer

2021 - 2022, Inc.
  • Developed and maintained multiple applications using React Native for mobile and web technologies, resulting in a robust and feature-rich product.
  • Improved the team's code management flow by managing PR reviews and peer programming, resulting in increased developer integrity and code quality.
  • Contributed to the team's efforts in increasing the project's test coverage to over 40% by writing comprehensive unit and integration tests.
  • Integrated Storybook and TypeScript into an existing JavaScript project, resulting in improved code sustainability and a better developer experience.
  • Designed and implemented a highly scalable business logic architecture for the application using Redux and Redux Saga, which resulted in efficient and maintainable code.
  • Built camera and video capturing, editing, and streaming features using the react-native-camera and react-native-video libraries, enhancing the app's functionality.
Technologies: React Native, iOS, Redux-Saga, GraphQL, Svelte, React, Redux, Mobile App Development, Web Development, Mobile Development, Web App Development, Cross-platform, Cross-platform App Development

Senior React Native and iOS Developer

2020 - 2021
  • Led a team of three developers in the development and maintenance of a React Native application from scratch, resulting in a fully functional and feature-rich app.
  • Designed a solid and efficient React Native and Redux (Thunk) infrastructure and codebase, resulting in a maintainable and scalable application.
  • Collaborated closely with the business team to review Figma design mockups, provide feedback, and develop new features for the app.
  • Integrated Storybook to create and test UI components, ensuring consistent and high-quality visuals.
  • Consumed GraphQL and REST API using a dedicated API client and networking repository, efficiently retrieving and storing data in the app's reducers using Thunk.
  • Integrated Realm for local database integration and management, allowing for offline functionality and data persistence.
  • Implemented integration with iOS native code in Swift using React Native's NativeEventEmitter and NativeModules, expanding the app's capabilities.
  • Designed and implemented performant animations using Reanimated 2, enhancing the user experience.
  • Wrote unit tests for components and reducers using a React testing library and Jest, ensuring the reliability and stability of the app.
Technologies: JavaScript, TypeScript, React Native, Redux, Redux Thunk, Figma, Mobile Development, Minimum Viable Product (MVP), Cross-platform, Cross-platform App Development, Storybook, React, Firebase, Firebase Cloud Functions, Firebase Cloud Messaging (FCM), Technical Leadership, Technical Architecture, Leadership

Senior iOS Developer

2020 - 2021
Webex Events (formerly Socio)
  • Maintained and developed the Socio event app and lead retrieval iOS applications using an MVVM design pattern, Agile Tribe-Model, Swift, GCD, Chime, Firebase, Realm, unit integration snapshot tests, and SwiftyMocky.
  • Led the development of a brand new iPad application using SwiftUI, The Composable Architecture (TCA), Combine, GraphQL (Apollo), Realm, Firebase, and the Swift Package Manager, resulting in a modern and innovative product.
  • Designed and implemented CI/CD pipelines using Fastlane-Bitrise to build, test, and distribute over 1,000 white-label apps, streamlining the release process.
  • Utilized code quality measuring and stability tools such as SonarCloud and BugSnag to ensure the reliability and stability of the apps.
  • Contributed to creating a testable architecture and helped to increase the project's test coverage by over 40%, resulting in a robust and well-tested product.
Technologies: Swift, iOS, Xcode, Jira, SwiftUI, Realm, Firebase, Model View ViewModel (MVVM), Amazon Chime, Combine, Bugsnag, GraphQL, Apollo, Figma, UIKit, Mobile Development, Mobile App Development, Firebase Authentication, Firebase Cloud Functions, Firebase Cloud Messaging (FCM), Firebase Realtime Database, Alamofire

React Web Developer

2020 - 2020
Webex Events (formerly Socio)
  • Expanded a web app to adapt to changes in the event sector due to the pandemic by supporting the front-end team.
  • Maintained and developed the Socio Event web application using technologies such as React, TypeScript, Agile-Tribe Model, Redux, Firebase, Material UI, and unit-integration-Jest snapshot testing, resulting in a reliable and feature-rich product.
  • Designed and implemented a Firebase Realtime Database with a highly optimized Firestore communication infrastructure, enabling efficient data synchronization and manipulation.
  • Created a testable architecture by writing business logic, reducer tests, and unit tests, ensuring the reliability and stability of the app.
  • Debugged and delivered a high-quality product within a web environment using tools such as the browser's developer console and debugging libraries.
Technologies: React, TypeScript, Jira, Redux, Firebase, Material UI, Jest, Figma, Web Development, Web App Development, Firebase Hosting, Firebase Authentication, Firebase Cloud Functions, Firebase Cloud Messaging (FCM), Leadership

React Native Developer

2019 - 2020
Arkadaşım Diyabet
  • Developed and maintained Arkadaşım Diyabet Karbonhidrat—Bolus Hesaplayıcı for both iOS and Android, resulting in a valuable tool for type 1 diabetes patients.
  • Led the project voluntarily to provide better carbohydrate and bolus calculation tools for type 1 diabetes patients.
  • Designed, developed, and launched the applications on the App Store and Google Play Store, making the app widely available to users.
  • Implemented Firebase Realtime Database for data storage and synchronization, enabling real-time data updates and offline functionality.
  • Designed a highly scalable and solid React Native and Redux (Thunk) app infrastructure, resulting in a maintainable and efficient codebase.
Technologies: React Native, TypeScript, JavaScript, Firebase, Redux, APIs, Mobile Development, Mobile App Development, Cross-platform, Cross-platform App Development, React, Firebase Realtime Database, Firebase Cloud Functions, Technical Architecture, Technical Leadership, Leadership

Senior iOS Developer

2019 - 2020
Bundle News
  • Developed new features and maintained and refactored the Bundle News iOS application, which has approximately one million monthly active users, resulting in an improved and up-to-date app.
  • Integrated mobile ad networks, including MoPub, Google Ad Manager (DFP), AdMob, and Facebook Audience Network, into the existing iOS application, expanding the app's monetization capabilities.
  • Maintained and developed features using Firebase tools such as Analytics, Crashlytics, Realtime Database, Storage, and Authentication, resulting in a reliable and feature-rich app.
  • Improved my skills in declarative programming paradigms using Swift and reactive programming technologies such as RxSwift and Cocoa-specific extensions.
  • Maintained and developed local storage using Realm and the built-in storage tools of Cocoa Touch, enabling efficient data management and persistence.
Technologies: Swift, iOS, Xcode, Realm, Firebase, Model View ViewModel (MVVM), RxSwift, Cocoa Touch, MoPub, Firebase Realtime Database, Firebase Authentication, Firebase iOS SDK, iOS Native Libraries, iOS SDK, Mobile App Development, Mobile Development, Leadership

iOS Developer

2019 - 2020
  • Built the initial prototype of Midas, a commission-free investing platform, which resulted in a functional and feature-rich app.
  • Developed various candle and line charts using technologies such as Charts and socket connections to visualize real-time data, thus enhancing the app's functionality and usability.
  • Established the UI infrastructure and network layer using technologies such as UIkit, Charts, Alamofire, and PromiseKit, resulting in a seamless and intuitive user interface.
  • Collaborated with the design team by reviewing mockups and providing feedback to inform the app's architecture and design.
Technologies: iOS, Swift, MVC Frameworks, Charts, Alamofire, PromiseKit, iOS SDK, iOS Native Libraries, UIKit, Mobile Development, Mobile App Development, Minimum Viable Product (MVP), Leadership

iOS Developer

2018 - 2019
  • Developed, published, and maintained's new iOS application (v5.0+), resulting in an up-to-date and feature-rich product.
  • Led the app's development from the design stage through market release, managing the process from Zeplin to the App Store.
  • Analyzed and maintained the app on the market to provide the best possible user experience.
  • Developed, published, and maintained iOS applications for the partners, expanding the company's reach and capabilities.
  • Specialized in Swift architecture and implemented best practices, software architecture designs, OOP, and design pattern principles, resulting in efficient and maintainable code.
  • Gained a strong understanding of Apple's and Google's interface guidelines and design principles, ensuring compliance and high-quality visuals.
  • Connected RESTful APIs to iOS applications and back-end services, enabling efficient communication and data manipulation.
Technologies: Swift, iOS, Xcode, MVC Frameworks, UIKit, iOS SDK, iOS Native Libraries, Alamofire, Mobile App Development, Mobile Development, Technical Architecture

Junior iOS Developer

2017 - 2018
  • Gained strong engineering skills and programming fundamentals and a strong understanding of code versioning and source control tools.
  • Developed internal CocoaTouch frameworks and libraries for projects.
  • Gained a deep understanding of UIKit and animations in iOS.
  • Collaborated with teammates and provided always high motivation to all colleagues.
  • Constructed a strong foundation in software architecture design, OOP, design patterns principles, consumption of RESTful APIs, Swagger, Apple's interface guidelines and design principles.
  • Built a strong foundation on the Swift language architecture, features, and best practices.
Technologies: Swift, iOS, Xcode, MVC Frameworks, UIKit, Mobile Development, Mobile App Development

Socio Event App
With the goal of taking your event experiences to the next level, Socio is your new go-to app at events, serving as a networking tool and digital event guide.

Through its shake-and-connect technology, Socio gets rid of the hassle of exchanging contact information. Just link your email, phone number, and social media accounts to a single profile and connect with others by simply shaking your phone! Magic!

In addition, with Socio serving as a digital event guide, you can access all of the information surrounding the events you attend, like attendee lists, the agenda, and who the sponsors are. With just a few clicks, you can stay in the loop with every update and change.

Lead Retrieval by Socio
Lead Retrieval by Socio allows you and your booth staff to do the following:
• Scan attendee badges to capture leads
• Prioritize, qualify, and rate your leads by the level of importance
• Take notes, collaborate, and never miss a detail by working with your team
• Analyze the results and seamlessly export the leads you captured

Other Features:
• Works online and offline
• No hardware required
• Scan and collect from anywhere
• Tablet and mobile compatible
• Real-time reports and lead exports

Access to the app, Lead Retrieval, is managed by event organizers. If you are interested in using Lead Retrieval for your events, please visit to learn more.

Midas is the way to invest in Turkish and American stock exchanges with ease

Midas is a regularly audited brokerage house licensed by the Capital Markets Board of Turkey. Your money is kept safe due to the fact that your accounts are registered with the Central Registry Agency and Takasbank.

Bundle News
Bundle is the top-rated news aggregator, delivering news and events that matter to you.

All the news across the globe—discover the best stories from the top national news providers to local niche websites and blogs. Available for your personal collection, a selection of over 10.000 (and growing) news outlets, online publishers, magazines, newspapers, columns, and blogs from 18 countries. You’ll be informed and inspired by the world’s top publications, including The Guardian, TIME, The New York Times, Business Insider, Bloomberg, Mashable, and many more!

Obilet is the app to purchase bus and flight tickets in Turkey!

Obilet is Turkey's online bus ticket and flight ticket office. You can purchase tickets from hundreds of bus companies, especially Kamil Koç, Metro Turizm, Pamukkale Turizm, Ali Osman Ulusoy, Varan Turizm, Isparta Petrol, and Efe Tur, on Obilet. You can also buy domestic and international flight tickets from every airline company operating in Turkey, including Turkish Airlines (THY), Anadolu Jet, Pegasus, and Sun Express.

A special note, Obilet has been named Europe's best travel app by Mastercard!

Tosla is the easiest, fun, and social way to send money between friends. Plus it's free! With this, you send money to or request money from your friends no matter the time of day, shop securely from your favorite apps, online and in stores, and write and share in real-time the funniest notes with your friends!

TFX Target

With TFX Target, foreign exchanges, precious metals, stocks, and investment transactions are at your fingertips!

Perform 5/24 transactions by following the foreign exchange and precious metal movements simultaneously with the world markets. And follow and trade BIST stock and mutual fund transactions from anywhere at any time.

Connect your world with a super-efficient personal platform to organize, build and share your life with friends, families, and communities. Hoopt is a collection gathering platform that enables users to share and explore places, movies, and books with their very own community.

Arkadaşım Diyabet | Carbohydrate Bolus Calculator
It is now very easy to manage your diabetes. With the Carbohydrate-Bolus Calculator, you can calculate the carbohydrate values ​​of your meals drawing from our food list. You can quickly and easily calculate your insulin dosage after inputting what foods you've eaten.

REAL is an exciting and revolutionary new platform that allows creators to establish coins that fans can purchase to obtain more direct access to an exclusive and broad range of authentic content. REAL will be available at the launch through its website and a native iOS app.

Novus Writer
Novus is an AI-powered tool that streamlines content creation and produces original, high-quality content. With just a few words of input, Novus can generate written or visual content tailored to customers' specifications. Customers can adjust parameters, such as language, tone, and style, to get the perfect output. Novus has a built-in fact-checking module that verifies the accuracy of any claims made in the text. It searches online, reputable sources to find supporting or conflicting evidence and provides reliable references for any assertions.

Inner is a social decision-making app that connects users with their inner circle of up to 150 close friends and gives them personalized recommendations. Sharing suggestions and recommendations with the trusted network allows them to make informed decisions about shopping, movies, and places to visit. Inner has push notifications and a feature to save favorite recommendations.
2016 - 2019

Bachelor's Degree in Physics

Koç University - Istanbul, Turkey

2014 - 2019

Bachelor's Degree in Electrical and Electronics Engineering

Koç University - Istanbul, Turkey


React, Alamofire, PromiseKit, Firebase iOS SDK, Node.js, iOS Native Libraries, RxSwift, iOS Charts, Redux-Saga, Stripe, Stripe API


Xcode, Jira, Firebase Authentication, Firebase Cloud Messaging (FCM), Bugsnag, MoPub, Google Analytics, Figma, GitHub, Redux Thunk


React Native, UIKit, Cocoa Touch, iOS SDK, SwiftUI, Redux, Swagger, Combine, Jest, Svelte, Material UI, Express.js, Next.js


Swift, TypeScript, JavaScript, GraphQL


Model View ViewModel (MVVM), Testing, Unit Testing, Mobile Development, Reactive Programming, Cross-platform


iOS, Firebase, Cloud Run, Visual Studio Code (VS Code), Android


Realm, Firebase Realtime Database, Cloud Firestore


Computer Science, Software Development, Front-end, Firebase Cloud Functions, Technical Architecture, Leadership, Charts, Apollo, APIs, Minimum Viable Product (MVP), Storybook, Firebase Hosting, Technical Leadership, Amazon Chime, MVC Frameworks, Payment APIs, Mobile App Development, Web Development, Web App Development, Cross-platform App Development, Framer X, OpenAI, Stripe Payments, Google Cloud Functions, React Native Reanimated, Technical Support, Technical Design

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