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  1. Freelancers

Serhii Krainik

Offer Serhii work on your next project.

Ukraine Dnepr, Ukraine
8 months 7 days back
A little busy a little busy
age 33 years
on the service 3 years
  • Kotlin multiplatform
  • kmp
  • Flutter
Freelancer Serhii K. — Ukraine, Dnepr. Core skill — App Development for Android, Content Management Systems

Rating

Successful projects
No data
Average rating
No data
Rating
250
App Development for Android
131 place out of 341
Content Management Systems
225 place out of 706

Language proficiency level

Українська Українська: fluent
Русский Русский: fluent
English English: pre-intermediate

CV

I am a Senior Web & Mobile Developer with over 5 years of experience in developing web and mobile applications. I work as a full-stack developer, confidently navigating all stages of software creation — from architecture to deployment and maintenance.


Web Development

I have deep knowledge of PHP and JavaScript, specializing in WordPress development without using third-party plugins — I create custom functionality, themes, API integrations, and connections with external services. I also provide support and further development for existing projects.


Mobile Development

I develop Android applications in Kotlin using modern approaches — Jetpack Compose, MVVM, Coroutines, Room, Firebase. I also work with Flutter to create cross-platform solutions. I handle projects of any complexity — from MVPs to full-scale applications with integrations like Stripe, Apple Pay, Google Pay, maps, chats, rating systems, and more.


My portfolio includes:

-Business solutions for construction companies

-A car booking app in the USA

-A fuel delivery service in Kyiv

-Interactive office panels with room schedules

Skills and abilities

Programming

Mobile development

Portfolio


  • Proglass

    Web Programming
    Comprehensive work on transferring the website to a new hosting, translation using Google Translate because there was an unclear calculator and it was decided to use this translation option due to budget and time constraints, code correction, overall website refinement

  • Website for a cleaning company

    Web Programming
    Website from scratch on WordPress. A template was purchased for the IT theme. Only styles and some components were taken as a basis, the rest was redesigned. The template was built on ACF.

  • Ez CaRent

    Hybrid Mobile Apps
    Ez CaRent — example of freelancer's portfolio work in category Hybrid Mobile Apps
    This is a cross-platform mobile application built on Flutter for convenient car rental in the USA, particularly in Florida, Miami, and surrounding areas. It is an MVP solution that already includes core features for renters and car owners.

    The app allows users to easily find, book, and pay for a car directly from their smartphone using Google Pay, Apple Pay, or a card.

    … Technologies: Flutter, Dart, BLoC, Firebase, Dio, Clean Architecture, GetIt

  • RoomsKey

    App Development for Android
    RoomsKey — example of freelancer's portfolio work in category App Development for Android
    Roomskey — is a professional tool for construction and renovation companies that allows creating and managing projects from start to finish, involving a team of managers, performers, and clients.
    The app provides efficient collaboration, transparency at every stage, and convenient management of all documentation in digital format.

    Main features:
    …
    Creating projects with the ability to add participants with different roles

    Maintaining detailed reports: photos, videos, comments, progress assessments

    Exchanging text messages in the built-in chat

    Managing tasks and implementation stages

    Full history of changes and control over work status

    Advantages:

    Centralized management of all project information

    Simple interaction between all parties — from performers to clients

    Transparent reporting and archive of all actions

    Suitable for both large construction companies and small teams

    Technologies: Kotlin, Jetpack Compose, Ktor, Coroutines, MVVM, Room, Firebase
  • 226 USD

    Quick hub

    App Development for Android
    Quick hub — example of freelancer's portfolio work in category App Development for Android
    Information panel for room booking (tablet application)
    This application was developed specifically for tablets using modern native development technologies on Android. Its main purpose is to serve as an information panel in the office to display current bookings of conference rooms, as well as show their availability.

    Up to 4 such tablets can be installed in the office — each responsible for a separate room.
    … The user can interact with the interface: view the booking schedule using scrolling or a slider.

    Bookings are made through a website, and the application operates 24/7, providing only visualization of current information without the ability to make changes from the device.

    Technologies: Kotlin, Jetpack Compose, XML, Ktor, Coroutines, MVVM.

  • Didido

    App Development for Android
    Didido — example of freelancer's portfolio work in category App Development for Android
    An app for diesel delivery in Kyiv, which will be available in other regions in the future.
    The app's feature is that the customer can order diesel as if ordering a taxi — and within 2 hours, the fuel will be delivered, or, if needed, delivery can be scheduled for another date.
    The customer can track the delivery in real-time — just like in taxi services. Payment is made through FOP or LiqPay.
    Personal data verification is also implemented via BankID using PrivatBank or monobank.
    …
    Technologies used: Kotlin, Compose, XML, Retrofit 2, Coroutines, MVVM, Room, Google Maps, Firebase, BankID
  • 158 USD

    Calendar of Notes

    App Development for Android
    Calendar of Notes — example of freelancer's portfolio work in category App Development for Android
    Calendar of notes. The client used the compose and database firebase. and characteristics. Full visual control over the application through the database, the processing of a large amount of photos. Remembrance of yourself, reminder of yourself.
    There will be a new version for Poland.
  • 113 USD

    Searching for low prices

    App Development for Android
    Searching for low prices — example of freelancer's portfolio work in category App Development for Android
    Application to search for low prices, in local product network stores. Features, fast access to the applied networks, convenient view of the goods of 5 networks in one place. Available in Macket. Composite and Composite. WebView
  • 90 USD

    Generator of ideas for cooking food from having products

    App Development for Android
    Generator of ideas for cooking food from having products — example of freelancer's portfolio work in category App Development for Android
    The application is based on AI chat gpt 3. and characteristics. Integration of apps with chat gpt 3.
    Coltin, Compose, Room and Ktor.

Activity

  Latest proposals 10
Corrections in the mobile application
500 USD
Build APK for Android
34 USD
Android Studio Task
29 USD
WordPress Update - 6.8.1 and WooCommerce 9.8.5
34 USD
Application for Android and iOS
21 USD
Transfer the website and edit the content
87 USD
Application for the master’s services
23 USD
Insert pixel on the website
16 USD
Remote assistant for WordPress and content (15–20 hours/week)
999 USD
UPGRADE of the website on Wordpress
16 USD