Cesar David Sosa Perez, Developer in Madrid, Spain
Cesar is available for hire
Hire Cesar

Cesar David Sosa Perez

Verified Expert  in Engineering

Mobile App Developer

Location
Madrid, Spain
Toptal Member Since
September 13, 2022

Cesar is a full-stack software engineer specializing in React Native, Kotlin, and Swift. His broad experience includes developing essential applications in various sectors such as banking, telecommunications, health, and artificial intelligence (AI). Cesar's important area of interest is working with Agile methodologies with CD/CI and the cloud.

Portfolio

Carrier - Residential - Mobile Apps Product Management
Swift, JavaScript, Objective-C, React Native, Architecture, Mobile UX, Apollo...
Chasing Bacon LLC
Swift, Kotlin, iOS, Android, PHP, Laravel, Vue, Docker, jQuery...
Tata Consultancy Services
React Native, Expo, Ionic, Django, Android, iOS, Node.js...

Experience

Availability

Part-time

Preferred Environment

React, Android, Swift

The most amazing...

...features I've developed are new features for BBVA and Santander Bank financial web/apps.

Work Experience

Swift Developer (via Toptal)

2024 - 2024
Carrier - Residential - Mobile Apps Product Management
  • Developed a cross-platform mobile application using React Native, achieving a 20% increase in user engagement within the first three months.
  • Implemented Redux for state management, reducing app crashes by 35% and improving overall app performance.
  • Led a team to integrate push notifications and in-app messaging, resulting in a 15% boost in user retention and a 10% increase in daily active users.
Technologies: Swift, JavaScript, Objective-C, React Native, Architecture, Mobile UX, Apollo, Node.js, GraphQL, SwiftUI, Plaid, Mobile Architecture, React Query, tRPC

Swift and Kotlin Developer

2023 - 2023
Chasing Bacon LLC
  • Refactored and developed new functionalities in Android native app using Kotlin, MVVM, push notifications, and Firebase Authentication.
  • Built and refectored new functionalities in the iOS native app using Swift, SwiftUI, MVVM, push notifications, and Firebase Authentication.
  • Developed new functionalities in the REST API using PHP and Laravel, implemented in AWS.
Technologies: Swift, Kotlin, iOS, Android, PHP, Laravel, Vue, Docker, jQuery, Test-driven Development (TDD), React Navigation, Emotion Library, Mobile UX, DevOps, Microfrontends, SwiftUI, Stripe API, Plaid, Progressive Web Applications (PWA), OpenAI, Messaging, Networks, Software, Technical Writing, Figma, Mobile Architecture, tRPC, Containers, Apple Subscriptions, Stripe Subscriptions, Subscriptions

Full-stack Software Engineer

2022 - 2023
Tata Consultancy Services
  • Refactored a React Native app to use Redux, Context, and reducers instead of isolated states around the app.
  • Developed new Ionic functionalities in TypeScript.
  • Led a new feature development, preconfigured dashboards, which integrate applications developed in Ionic, React Native, Django, and BigQuery.
Technologies: React Native, Expo, Ionic, Django, Android, iOS, Node.js, Application State Management, Responsive Web Apps, TypeScript, HTML, AWS Cloud Architecture, Redux, Mobile, Mobile Development, APIs, Front-end Development, Google Cloud Platform (GCP), Full-stack Development, Microservices Architecture, Hybrid Frameworks, Amazon DynamoDB, Stripe, MongoDB, Web Development, Instant Messaging, Full-stack, AI Programming, User Interface (UI), Python, Back-end, SQL, Material UI, Microservices, Amazon RDS, REST APIs, API Gateways, Amazon Simple Queue Service (SQS), Kubernetes, Architecture, Abstraction, Vue, PHP, Docker, jQuery, Test-driven Development (TDD), React Navigation, React Router, Emotion Library, Mobile UX, Cloud, DevOps, Next.js, Heroku, ASP.NET Core, React Final Form, OWASP, Microfrontends, Stripe API, Progressive Web Applications (PWA), Apache Maven, Data Engineering, Scala, Blockchain, Messaging, Networking, Software, Technical Writing, Telerik, Rails Engines, Figma, Webflow, Containers, WordPress

Full-stack Software Engineer

2021 - 2022
Electronic IDentification (eID)
  • Developed new Angular, React, and Java functionalities.
  • Coordinated using WebRTC protocols for real-time video in the Android, iOS, and JavaScript SDKs.
  • Created the pipelines in GitLab for iOS and Android using Gitlab runners and AWS.
  • Led new product development, CertID, using NFC reader in Android and iOS using ICAO standard.
Technologies: Kotlin, Android, iOS, Swift 5, Angular, Java, Spring 4, Stripe Connect, REST APIs, HTML, Amazon Web Services (AWS), TestFlight, Mobile, Mobile Development, APIs, Firebase, Google Cloud, Front-end, Front-end Development, Android SDK, SDK Development, SDKs, Full-stack Development, Microservices Architecture, Hybrid Frameworks, Xcode, Swift 4, iOS SDK, Near-field Communication (NFC), Web Development, Early-stage Startups, CSS, TypeScript, Serverless, Full-stack, AI Programming, User Interface (UI), User Experience (UX), Python, Tailwind CSS, SQL, GraphQL, Over-the-top Content (OTT), Android TV, Microservices, Amazon RDS, API Gateways, Amazon Simple Queue Service (SQS), Kubernetes, Terraform, Architecture, Abstraction, Docker, jQuery, Test-driven Development (TDD), React Navigation, Emotion Library, Mobile UX, Cloud, API Integration, ASP.NET Core, Speech to Text, Amazon Elastic MapReduce (EMR), Apache Airflow, Networking, cPanel, Platforms, Telerik, Containers, WordPress, Vercel

Senior Developer

2020 - 2021
Amaris Consulting
  • Developed a CE-marked medical app for multiple sclerosis patients to assess neurological functions using novel digital biomarkers focused on movement, balance, dexterity, and vision.
  • Applied Scrum methodology to coordinate with international UK, US, and EU teams.
  • Created Jenkins Pipelines in cloud for deployments .
Technologies: Android, iOS, REST APIs, Mobile App Development, Mobile Security, Mobile, Mobile Development, APIs, Firebase, Google Cloud, Front-end, Front-end Development, Android SDK, SDK Development, SDKs, Android Studio, Xcode, Stripe Payments, Web Development, TypeScript, Full-stack, User Experience (UX), Tailwind CSS, Web Design, Over-the-top Content (OTT), Android TV, Amazon Simple Queue Service (SQS), Jenkins, Architecture, Docker, jQuery, Heroku, API Integration, ASP.NET Core, Audio, Blockchain, cPanel, Platforms, Spring, WordPress

Senior Developer

2019 - 2020
AXPE Consulting
  • Built the SAN Shareholders and Investors Android and iOS apps for Santander Group, distributed via Google Play and AppStore.
  • Developed new features for the "Mi Vuelta" COVID-19 app in React Native.
  • Enabled the login integration of the Crisis app in Ionic 4.
Technologies: Android, iOS, JavaScript, TypeScript 3, React Native, Ionic, REST APIs, MySQL, Encryption, User Permissions, TestFlight, Mobile App Development, Mobile Security, Flutter, Mobile, Mobile Development, APIs, Firebase, Google Cloud, Android SDK, SDK Development, Microservices Architecture, Hybrid Frameworks, Android Studio, Stripe Payments, Serverless, Jenkins, Architecture, Scalability, Mobile UX, Swift, API Integration, DigitalOcean, Technical Writing, Spring, Redis Cache

Technical Consultant

2018 - 2019
Stefanini Group
  • Led the mobile development for the BBVA NetCash app QR payments project.
  • Managed the SWIFT transfers tracking project for the BBVA NetCash app.
  • Solved the incidents reported by the ethical hacking assessment for Android and iOS apps.
Technologies: Android, iOS, .NET Core, User Permissions, Mobile App Development, Mobile Security, Mobile, Mobile Development, APIs, Android SDK, Hybrid Frameworks, Microsoft SQL Server, Objective-C, Web Design, Blazor, Back-end, SQL, Architecture, Scalability, DigitalOcean, Spring Boot, Django, Ruby, Redis Cache

Technical Lead

2016 - 2018
Inca Garcilaso de la Vega University
  • Led the development of a tourist application, through machine learning and big data, recognizing monuments of the main cathedrals of Lima, working in real-time using mobile devices' cameras.
  • Visited Bucharest, Romania, to receive training in big data and machine learning at the Polytechnica University of Bucharest as part of the UMETECH project.
  • Developed and managed the new app for getting familiar with most touristic routes in Lima, Peru, as part of the arrangement with the Lima city council.
Technologies: Android, .NET, C#, SQL, PostgreSQL, C#.NET, MySQL, User Permissions, Mobile, Mobile Development, APIs, Front-end Development, Android SDK, Laravel, Microsoft SQL Server, VBScript, Web Design, Back-end, Ruby on Rails 2, Spring Boot, Ruby

Full-stack Developer

2014 - 2016
Inca Garcilaso de la Vega University
  • Built the university app for more than 40 thousand students.
  • Defined the solution architecture using ASP.NET services, SQL, and MySQL databases.
  • Developed new features for the students' and teachers' internal enterprise resource planning (ERP) using CakePHP, MySQL, and SQL.
Technologies: PHP, JavaScript, jQuery, ASP.NET, SQL, MySQL, C++, Mobile, APIs, Front-end Development, Laravel, CSS, Visual Basic for Applications (VBA), Active Server Pages (ASP), Blazor

IMAP Portal

https://imap.windowbook.com/
A cloud-based solution code in Angular .NET Core for the back end,
it allows Windowbook clients (mailers) to have a complete view of their undocumented postage statements from USPS (postal service of the US).

I designed and developed the project from scratch and created the CD/CI process in AWS using Bitbucket pipelines, Amazon ECS, Amazon CloudFront (CDN), and Amazon Route 53.

Movistar Smart WiFi

https://play.google.com/store/apps/details?id=com.movistar.co.base&hl=en&gl=US
A Kotlin-based app used by more than one million users in Spain, Brazil, and other countries,

This app allows users to manage their Telefonica router in their homes with options like limiting access to specific devices according to timeframes or improving speed for other devices.

I participated in developing a new feature named GamingOn, which allows the user to open ports for specific gaming platforms like Fornite using the mobile phone.

Financial App for an Important Bank

https://play.google.com/store/apps/details?id=pe.bbvacontinental.netcash
A Koltin financial app in which the user could see the global position, accounts, payment services, etc.

I participated in developing two new features: Swift tracking and international tracking of transfers. QR payments enable the business client to start receiving payments using the BBVA Netchash app. I acted as the Android/iOS lead and developer.

Canary - Smart Home Security

https://play.google.com/store/apps/details?id=is.yranac.canary&hl=en&gl=US
A Kotlin-based mobile app built on the MVVM Clean architecture, their app improves security in homes around the world using IoT devices like cameras and other devices.

This application lets users see all the cameras installed in their homes in real time and notify them when a person enters their house when the user is out. The application sends the video to the machine learning detection process in Cloud.

SAN Shareholders and Investors App

https://play.google.com/store/apps/details?id=es.bancosantander.accionistas&hl=en&gl=US
The app is available in Spanish and English. It offers different functionalities, such as real-time shares prices in all the markets where Santander operates, historical shares info with interactive graphics about evolution and peer comparison, and information about dividend payments and other corporate operations.

Healios+Me

https://apps.apple.com/es/app/healios-me/id1572967523?l=en
Healios+Me supports neurology research, helping people diagnosed with multiple sclerosis or related conditions.

Open the app regularly to complete a range of tasks, challenges, and games wherever you are. We use data from your phone's sensors and integration with Apple Health and HealthKit, and analyze it using our cutting-edge algorithms for digital biomarkers.

VideoID

https://www.electronicid.eu/en/solutions/videoid
SDK and back-end support for the real-time identification onboarding process, working using video streaming technology and machine learning. VideoID works asynchronously, through substantial registration and agent verification, and synchronously through videoconference interviews.

Tourism App

A Kotlin/Java application for tourism, which helps users visit the main routes of Lima, Peru. The application was developed in coordination with the city of Lima.

TOOLS:
• Google Map integration
• MVVM
• Jetpack

Toptal Node.js Accelerator

The Node.js Accelerator is an exclusive learning program that educates JavaScript/back-end developers in Node.js, Express.js, NestJS, and TypeScript. This is a 2-month program that consists of rigorous learning exercises, live instructor-led sessions by SMEs, hands-on activities, a stringent evaluation process, comprehensive assessments, and an incremental project where participants implement a couple of microservices (REST APIs) using Express.js and NestJs. The incremental project simulates an eCommerce application consisting of two services, i.e., a user service to implement the authentication with user management and a product-catalog service that offers functionalities to manage inventory.
2005 - 2010

Bachelor's Degree in Computer Science

National University of San Marcos - Lima, Peru

DECEMBER 2022 - PRESENT

Toptal Node.js Accelerator Graduate

Toptal, LLC

NOVEMBER 2021 - PRESENT

AWS Certified Cloud Practitioner

Amazon Web Services

NOVEMBER 2020 - NOVEMBER 2022

Certified Scrum Master

Scrum Alliance

NOVEMBER 2019 - PRESENT

Associate Android Developer

Google Developers

Libraries/APIs

React, jQuery, Node.js, REST APIs, Retrofit, Alamofire, Vue, React Navigation, React Router, Stripe, React Final Form, Stripe API, Rails Engines, React Query, Apple Subscriptions, Stripe Connect, CocoaPods, Emotion Library

Tools

Jira, Confluence, TestFlight, GitHub, Git, Bitbucket, Android Studio, Xcode, Jenkins, Amazon SageMaker, Terraform, Plaid, Amazon Elastic MapReduce (EMR), Apache Airflow, Apache Maven, Figma, TargetProcess, Trello, Expo, Amazon Elastic Container Service (Amazon ECS), Amazon CloudFront CDN, Docker Compose, Amazon Simple Queue Service (SQS)

Frameworks

Angular, React Native, .NET, .NET Core, Dagger 2, Android SDK, Laravel, iOS SDK, Next.js, Tailwind CSS, Blazor, ASP.NET Core, SwiftUI, Django, ASP.NET, Redux, Ruby on Rails (RoR), Material UI, Ruby on Rails 2, Spring, Spring Boot, tRPC, Ionic, Express.js, Spring 4, Flutter, .NET 5, NestJS

Languages

Kotlin, Java, JavaScript, Clean, C#, SQL, PHP, TypeScript, Swift, Swift 4, Objective-C, CSS, VBScript, Visual Basic for Applications (VBA), Active Server Pages (ASP), Python, Ruby, HTML, C#.NET, C++, GraphQL, Swift 5, TypeScript 3, Scala

Paradigms

Model View ViewModel (MVVM), Clean Architecture, Unit Testing, Mobile Development, Microservices Architecture, Microservices, Object-oriented Programming (OOP), Best Practices, Test-driven Development (TDD), Microfrontends, Agile, Scrum, DevOps

Platforms

Android, iOS, Amazon Web Services (AWS), Docker, Mobile, Firebase, Android TV, Software Design Patterns, Kubernetes, cPanel, WordPress, AWS Lambda, Google Cloud Platform (GCP), Heroku, DigitalOcean, Telerik, Webflow, Vercel, Amazon EC2, Blockchain

Storage

Amazon S3 (AWS S3), Google Cloud, Amazon DynamoDB, Microsoft SQL Server, PostgreSQL, MySQL, MongoDB, Redis Cache

Industry Expertise

Web Design

Other

User Permissions, Mobile App Development, Mobile Security, UI Testing, Pull Requests, APIs, Front-end Development, SDK Development, SDKs, Full-stack Development, Hybrid Frameworks, Near-field Communication (NFC), Web Development, Early-stage Startups, Serverless, Full-stack, User Interface (UI), User Experience (UX), Back-end, Over-the-top Content (OTT), Amazon RDS, Architecture, Mobile UX, Cloud, Networking, Software, Mobile Architecture, Subscriptions, Application State Management, Responsive Web Apps, AWS Cloud Architecture, Encryption, Front-end, Stripe Payments, Instant Messaging, AI Programming, PSD to Swift, Abstraction, Scalability, API Integration, Audio, Speech to Text, OWASP, Progressive Web Applications (PWA), Messaging, Networks, Platforms, Technical Writing, Containers, Stripe Subscriptions, Scrum Master, Autoscaling Groups, Load Balancers, Data Compression, Code Review, CI/CD Pipelines, API Gateways, Apollo, OpenAI, Data Engineering

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.

1

Share your needs

Discuss your requirements and refine your scope in a call with a Toptal domain expert.
2

Choose your talent

Get a short list of expertly matched talent within 24 hours to review, interview, and choose from.
3

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