Modernizing a legacy enterprise messaging app for secure corporate communication

Our customer is an established provider of secure enterprise communication tools. They serve organizations that rely on stable internal messaging to keep their teams connected. Their main product is an enterprise messaging platform that supports real-time collaboration, file sharing, and user management across an organization. Around the messaging service, the company also provides native mobile apps, a browser-based web app, and a central admin console, making the platform a reliable way for modern enterprises to communicate. 

Business challenge

For all its value to their clients, the platform behind our customer's enterprise messaging app had started to fall behind current standards as it grew. The technology it was built on was getting outdated.

The main problem was technology debt. The code used outdated libraries that were hard for developers to learn and risky to change, since even a simple bug fix could break something else. Working on that aging stack also wore down the team over time. The platform also had needs that could not be dropped. The web app still had to run across many browsers, from modern ones to Internet Explorer, and the system had to move to central login through Single Sign-On (SSO) to meet current enterprise security standards.

What made the project hard was the balance the customer had to strike. They wanted to update the system while keeping risk and cost low, and without ever taking down a product their users relied on every day. They did not have the right skills in-house, so they looked for a reliable partner. With strong experience in enterprise system modernization and lab-type offshore development, VNEXT took on the work: rebuilding the base of the enterprise messaging platform while keeping it fully running the whole time.

Solution delivered

VNEXT updated the platform to Java 17 and reworked the architecture to clearly separate the controller, business logic, and service layers. We built on what was already there instead of starting over, which made the enterprise system easier to maintain and extend. The result is a lasting DX solution rather than a short-term fix. 

Modular architecture

We split the system into three main modules to make development and deployment simpler:

• Ic2-core: A shared library that holds core utilities, the MongoDB access layer, user management logic, and system settings. It also handles heavier tasks such as file uploads, using Jakarta-compatible versions of common libraries.
• Ic2-api: The main engine, which provides REST API endpoints, the web chat interface, and the login and permission layer. This module runs real-time messaging and connects to Spring Security SAML2.
• Ic2-ctl: A full control panel that lets administrators manage the dashboard, user groups, CSV imports and exports, and push notification settings for mobile devices.

Advanced communication features

We built the platform to support the ways modern enterprises communicate:

• Talk rooms: Beyond one-on-one chats, users can create group "talk rooms" for a project or department. Even when someone joins a room late, they can still see the full chat history.
• Broadcast functionality: The system can send a message to up to 10,000 users at once, including text, images, and attachments.
• Rich media sharing: Users can upload and share files, images, and videos easily.
• Smart notifications: We added real-time push notifications for both iOS and Android so users never miss an urgent update.
• Multi-language support: Japanese, English, Korean

Security and performance

To meet enterprise security needs, we added Spring Security SAML2 to provide a central SSO login. For reliable data, we set up MongoDB in a Primary/Secondary configuration with hot replication, which keeps the system fast and available even when part of the infrastructure fails. 

Technologies & Tools

Backend: Java 17, Apache Struts (custom Jakarta), Spring Framework, Spring Security SAML2, Log4j, Commons libraries, Jakarta Servlet/JSP API

Frontend: JavaScript (ES5/ES6), jQuery, jQuery UI, Quill.js (rich text editor), Tribute.js (mentions), JSP, HTML5/CSS3

Database: MongoDB (Primary/Secondary configuration with hot replication)

Mobile: iOS (Objective-C), Android (Java)

Windows App: C# (WinForms)

Notifications & Services: Push: Pushy, JavaPNS (iOS), FCM, Google Auth Library (Android); Email: Jakarta Mail; JSON: JSONic, JSON-lib; HTML parsing: Jericho

Build & Deploy: Maven, WAR packaging, multiple deployment profiles (integration, staging, production), JBoss/WildFly

Team scale

To deliver the project and ensure maximum system stability, we mobilized a dedicated team of six senior developers, each with 4  to 5 years of experience across legacy backend maintenance and modern multi-platform development. The team was structured to cover the full development lifecycle:

• Project Manager: planning, execution, web management, and technical solutions for client requirements
• Bridge Software Engineer (BrSE) / Business Analyst: BRD and SRS documentation, task assignment, tracking, and reporting
• iOS Developer: mobile app development on iOS using Flutter, Swift, or Objective-C
• Android Developer: mobile app development and deployment on Android using Java
• Bot Developer: chatbot design and implementation using Node.js
• QA Engineer: detailed test cases and execution to ensure quality before delivery

Process

Before development began, our team thoroughly analyzed the project requirements, with business analysts defining the solution concept and target audience. We followed Scrum with bi-weekly sprints to handle scope changes and keep steady progress. Tasks were tracked through the customer's backlog, with our Bridge Software Engineer (BrSE) responsible for assignment, tracking, and reporting. All client communication ran through Slack, including daily meetings to review progress and report interim outcomes.

We documented the client's vision in formal Business Requirement Documents (BRD) and Software Requirement Specifications (SRS), then continuously refined those requirements and broke them into tasks and subtasks for easier tracking. To ensure quality, developers confirmed features with the BrSE and followed a strict code review after every bug fix. Once a set of tasks was completed, our QA engineers wrote and ran detailed test cases to verify the solution met the requirements and was bug-free. This structured offshore development process let us ship regular updates while keeping the system stable and reliable.

Business outcome

VNEXT stabilized and modernized the client's enterprise messaging platform without interrupting their ongoing business operations, turning a long-running legacy system into a secure, maintainable foundation that continues to serve users every day.

Delivered through our lab-type offshore development model, the project produced the following business outcomes:

• Improved scalability and stability: the reorganized architecture significantly reduced the time needed to build new features and handle change requests, 
• Enhanced security: centralized Single Sign-On (SSO) protects corporate data while simplifying the login experience for users
• High availability: a MongoDB primary/secondary replication strategy keeps the system running with minimal downtime, even during infrastructure failures
• Communication at scale: the platform can broadcast a single message to up to 10,000 users at once, including text, images, and attachments
• Lower cost and faster time to market: modernizing the existing platform instead of rebuilding it from scratch optimized costs and sped up delivery of new functionality
• Reusable technical foundation: a standardized technology stack and build-deploy process created a sustainable base that can be reused for future enterprise solutions with similar requirements

The platform now serves as a primary tool for enterprise messaging across large organizations, providing a secure, multi-language environment in Japanese, English, and Korean for modern professional communication.