Damien is available for hire

Damien Doumer Kake

Verified Expert in Engineering

Software Engineer and Developer

Paris, France

Toptal member since January 23, 2024

Expertise

API Back-end Developers Full-stack Technical Writing Flutter Xamarin C#.NET Visual Studio Development JSON Microservices Development

Bio

Damien is an experienced software engineer who focuses on offering real-world solutions for complex ideas and problems. He is well-versed in turning plans into impactful, robust, well-architected, and fault-tolerant software systems. Damien's technology skills include Flutter, .NET, ASP.NET Core, Xamarin, and .NET MAUI.

Portfolio

Independent Freelancer

.NET MAUI, Flutter, ASP.NET Core, JSON, REST

YouScribe (The Netflix for Books)

.NET 7, ASP.NET Core, Flutter, Xamarin, C#, CQRS, OpenID Connect (OIDC)...

Kickle

.NET Core, Xamarin, Angular, Electron, C#, TypeScript, Git, API Development...

Experience

Xamarin - 8 years
ASP.NET Core - 8 years
.NET - 8 years
Flutter - 8 years
Mobile Development - 8 years
Back-end Development - 8 years
.NET MAUI - 4 years
OpenAI - 1 year

Availability

Part-time

Preferred Environment

.NET, ASP.NET Core, Flutter, Xamarin, Back-end, Mobile, C#, API Development, OpenAI, .NET MAUI

The most amazing...

...app I've built is YouScribe, a Netflix-like platform offering books used by millions of users, primarily located in France and French-speaking countries.

Work Experience

Senior .NET Mobile and Back-end Engineer

2024 - PRESENT

Independent Freelancer

Developed from scratch the Laba app (the best GPS app for leisurely rides and soft mobility.).
Led the development of ai4bio, AI + an awesome SAAS. ai4bio helps laboratories perform analytics on cellular images thanks to AI.
Contributed sample .NET MAUI demo apps showcasing how developers worldwide could use MAUI to build beautiful apps.

Technologies: .NET MAUI, Flutter, ASP.NET Core, JSON, REST

Back-end and Mobile Software Engineer

2020 - 2024

YouScribe (The Netflix for Books)

Acted as a mobile and back-end senior engineer for YouScribe, a company known as the Netflix for books. It has thousands of text and audiobooks, and users can stream, download, and consume the content on a subscription basis.
Maintained the YouScribe app and reduced its crash rate by more than 90%. Increased the overall rating frequency by over 50% and optimized it for speed and reliability.
Led a team while migrating YouScribe's legacy back-end infrastructure from ASP.NET to ASP.NET Core with microservices, clean architecture, OpenID Connect (OIDC), etc.
Architected the new back-end platform, leveraging a microservices architecture, clean architecture, CQRS, OpenID Connect (OIDC), and ASP.NET Core.
Led a team of two engineers in the 2nd migration of the YouScribe app to Flutter from Xamarin.Forms.
Optimized the back end for speed and reliability, including correcting bugs and rewriting several components for optimization.
Led the migration of YouScribe's mobile app from Xamarin Native to Xamarin.Forms.
Upgraded the platform's authentication system and built a compatibility layer to link legacy clients with new microservices in a reliable way.
Implemented native Kotlin/Java and Objective-C/Swift features using platform channels in Flutter.
Maintained and evolved some of YouScribe's back-end services.

Technologies: .NET 7, ASP.NET Core, Flutter, Xamarin, C#, CQRS, OpenID Connect (OIDC), Microservices Architecture, Clean Architecture, Xamarin.Forms, Git, API Development, SQL, Back-end, Mobile Apps, C#.NET, Visual Studio, Android, iOS, Mobile Development, Back-end Development, API Design, Microservices, Cross-platform, Full-stack, Software Engineering, .NET, ASP.NET, APIs, Entity Framework, App Development, Azure DevOps, Azure, Mobile Applications, Back-end Architecture, Full-stack Development, Google Cloud, MySQL, MongoDB, PostgreSQL, Dapper, Test-driven Development (TDD), Redis Cache, RabbitMQ, CI/CD Pipelines, Entity Framework Core, MediatR, Firebase, REST APIs, .NET Core, JSON, REST

Full-stack Software Engineer

2019 - 2020

Kickle

Worked as a full-stack software engineer for Kickle. This company builds meeting software such as collaborative whiteboards, video conferencing, etc, using ASP.NET Core and Angular with Electron for its desktop app.
Implemented real-time communication with client apps, using SignalR in ASP.NET Core and Angular; this feature was required for real time collaboration on the whiteboard software. Users could draw in real-time and interact together.
Added data caching with Redis. This was required to rapidly communicate between the microservices and save the real-time connection and data shared via SignalR.
Intervened by creating microservices with ASP.NET Core and implementing domain-specific features in a team of three back-end engineers.
Worked as a lead mobile developer on Kickle's mobile app, part of its meeting software pack.
Leveraged TypeScript to add features to the Angular web app.
Worked with Electron and OS-specific features (Windows and Linux), including process management, file access, installers, registry management, and services management.

Technologies: .NET Core, Xamarin, Angular, Electron, C#, TypeScript, Git, API Development, SQL, Back-end, ASP.NET Core, Clean Architecture, Mobile Apps, C#.NET, Visual Studio, Android, iOS, Back-end Development, API Design, Microservices, Cross-platform, Full-stack, Software Engineering, .NET, Microservices Architecture, APIs, Entity Framework, Flutter, JavaScript, TypeScript 3, Angular 7, App Development, Azure DevOps, Azure, Mobile Applications, Front-end, Full-stack Development, RESTful Microservices, SignalR, Redis Cache, RabbitMQ, CI/CD Pipelines, Entity Framework Core, MediatR, Firebase, REST APIs, JSON, REST

Back-end and Mobile Software Developer

2019 - 2019

HKB Ventures

Built a mobile back-end MVP for this client's startup. This MVP was an app for users to ship products, leveraging maps and real-time data.
Developed a mobile app where users could monitor the location of other users to deliver parcels in real time.
Created a back-end API with ASP.NET Core, offering authentication, CRUD operations, and real-time client communication.

Technologies: .NET Core, Xamarin, C#, Git, API Development, SQL, Back-end, Mobile Apps, C#.NET, Visual Studio, Android, iOS, Mobile Development, Back-end Development, Microservices, Cross-platform, Full-stack, Minimum Viable Product (MVP), Software Engineering, .NET, Microservices Architecture, APIs, Entity Framework, App Development, Azure DevOps, Azure, Mobile Applications, Back-end Architecture, Front-end, Full-stack Development, SignalR, CI/CD Pipelines, Entity Framework Core, MediatR, Firebase, REST APIs, JSON, REST

Back-end and Mobile Engineer

2018 - 2019

Infinite Square

Joined the team as a .NET back-end and mobile software engineer at Infinitesquare, a company that builds many SaaS products for many clients. They use Microsoft tech principally.
Built back-end software with ASP.NET Core, considering use cases specific to each client (Infinite Square's clients).
Worked with three developers to build cross-platform mobile applications with Xamarin.Forms.
Developed a Microsoft Teams bot leveraging Microsoft Graph API. This bot acted as a support agent for the Infinitesquare team.

Technologies: .NET Core, ASP.NET Core, Xamarin, C#, Xamarin.Forms, Microsoft Graph API, Git, API Development, SQL, Back-end, Mobile Apps, C#.NET, Visual Studio, Android, iOS, Mobile Development, Back-end Development, API Design, Microservices, Cross-platform, Full-stack, Minimum Viable Product (MVP), Chatbots, Software Engineering, .NET, Microservices Architecture, APIs, Entity Framework, App Development, Azure DevOps, Azure, Mobile Applications, Full-stack Development, CI/CD Pipelines, Artificial Intelligence (AI), Entity Framework Core, MediatR, Firebase, REST APIs, JSON, REST

Software Engineer

2017 - 2018

Freelance Software Engineer

Acted as a freelance independent developer and built software solutions for multiple clients, using .NET and C# as the primary technologies to make anything from desktop and mobile apps to bots.
Developed desktop apps with Windows Presentation Foundation (WPF) for client-specific scenarios.
Designed and built software to interact with specific user hardware, including the device's mouse and camera.
Created bots using Microsoft Bot Framework and mobile apps using Xamarin.Forms and Flutter.

Technologies: .NET, Xamarin, Windows Presentation Foundation (WPF), C#, Microsoft Bot Framework, Xamarin.Forms, Git, API Development, SQL, Back-end, Mobile Apps, C#.NET, Visual Studio, Android, iOS, Mobile Development, Back-end Development, Microservices, Cross-platform, Full-stack, Minimum Viable Product (MVP), Software Engineering, Microservices Architecture, APIs, Entity Framework, JavaScript, TypeScript 3, Angular 7, App Development, Azure DevOps, ChatGPT, Mobile Applications, Full-stack Development, Angular, Electron, AI Chatbots, Artificial Intelligence (AI), Entity Framework Core, Firebase, REST APIs, .NET Core, JSON, REST

Experience

Personal Blog

https://doumer.me/

As a passionate senior software engineer, I have created a blog that dives deep into various technical topics, code, web3 and crypto, and challenges through tutorials and articles read by hundreds of thousands of developers yearly. After having shared my knowledge consistently for years, I've received feedback from readers thanking me for the positive impact of my material on their daily professional lives.

Architected, Optimized, and Improved the Security of YouScribe's New Back End

As a senior lead developer at YouScribe (the startup that is the Netflix for books in Europe and Africa), I architected the whole back-end platform, led the migration from ASP.NET to ASP.NET Core, splitting monoliths into microservices, implemented microservices with CQRS, clean architecture, etc. I also built a secure authentication server with OpenID Connect (OIDC) and Duende, making it compatible with legacy clients. I also contributed to fixing bugs, optimizing the back-end infrastructure, and adding new features.

The YouScribe App

https://play.google.com/store/apps/details?id=youscribe.mobileapp

For about four years, I've been in charge of this app used in several countries, with a million users. I maintained and rebuilt the YouScribe app and then migrated the app to Flutter, lowering the crash rate by more than 80%. I improved user satisfaction and improved the rating by more than 50%. Before Xamarin's death, I led a team of three developers in migrating to Flutter. The YouScribe app is used primarily in France and several African countries. It enables users to stream/download and read books (PDF, EPUBs, and audiobooks). It has hundreds of thousands of users and millions of streams and reads monthly.

Maktabati

https://doumer.me/portfolio/maktabati-android-ios-app-at-youscribe/

The Maktabati app is made for Morocco citizens and was built in partnership with a company from Morroco. I built both the Android and iOS apps. They are available on phones and tablets. It is an app that provides kids in Morroco easy access to thousands of books. You can find it on Google Play Store and App Store.

Freechat

https://github.com/DamienDoumer/freechat

This is a sample open-source application built for the community of dotnet mobile developers (.NET MAUI and Xamarin). It showcases how to create a chat app with features such as message replies, navigation, beautiful UI, and much more.

Laba App, An App for Soft Mobility

https://labaapp.fr/

Built The best GPS app for leisurely rides and soft mobility. This app was required by a startup that wanted its idea implemented professionally and quickly. I built the platform from scratch and met the client's satisfaction.

Education

2014 - 2017

Bachelor's Degree in Computer Engineering

University of Buea - Buea, Cameroon

Certifications

OCTOBER 2019 - JULY 2022

Microsoft Most Valuable Professional (MVP)

Microsoft

MAY 2018 - PRESENT

Google Africa Challenge Mobile Web Specialist Course

Udacity

Skills

Libraries/APIs

API Development, REST APIs, Entity Framework, MediatR, SignalR

Tools

Visual Studio, Git, ChatGPT, Dapper, RabbitMQ

Languages

C#, C#.NET, Dart, SQL, TypeScript 3, JavaScript, TypeScript

Frameworks

.NET 7, ASP.NET Core, Flutter, .NET Core, .NET, ASP.NET, .NET MAUI, Entity Framework Core, Angular, Angular 7, Electron, Windows Presentation Foundation (WPF), .NET 8

Paradigms

Mobile Development, Microservices, Cross-platform, App Development, REST, Azure DevOps, Back-end Architecture, CQRS, Microservices Architecture, Clean Architecture, Test-driven Development (TDD)

Platforms

Xamarin, Android, iOS, Azure, Firebase, Microsoft, Microsoft Bot Framework, Mobile

Storage

JSON, MongoDB, PostgreSQL, Google Cloud, MySQL, Redis Cache

Other

Software Engineering, Back-end, Mobile Apps, API Design, Back-end Development, Full-stack, Minimum Viable Product (MVP), APIs, Mobile Back-end, Mobile Applications, Full-stack Development, Technical Writing, OpenAI, CI/CD Pipelines, Web3, Community, Computer Engineering, OpenID Connect (OIDC), Xamarin.Forms, Microsoft Graph API, Optimization, Cloud, Native Mobile Apps, Mobile App Development, Chatbots, Front-end, AI Chatbots, Web Development, RESTful Microservices, Artificial Intelligence (AI)

Collaboration That Works

How to Work with Toptal

Toptal matches you directly with global industry experts from our network in hours—not weeks or months.

Share your needs

Discuss your requirements and refine your scope in a call with a Toptal domain expert.

Choose your talent

Get a short list of expertly matched talent within 24 hours to review, interview, and choose from.

Start your risk-free talent trial

Work with your chosen talent on a trial basis for up to two weeks. Pay only if you decide to hire them.

Top talent is in high demand.

Start hiring