The existing POS system was built primarily on VB6 and Access. As it absorbed years of business process changes, its structure became increasingly complex, making feature additions and maintenance more difficult. Even when the company wanted to address new business requirements or improve operations, assessing the scope of impact required significant effort, forcing teams to approach changes with caution.

Because POS is a core system used every day in store operations, it must run reliably even offline and integrate correctly with multiple peripheral devices. The modernization therefore had to proceed while accounting for the constraints of each peripheral device and maintaining consistency with existing operations.

In addition, it was important not only to replace the existing system, but also to build a foundation that would make future expansion and maintenance easier. Rather than simply recreating current functionality in the short term, the project required an architecture that would remain easy to operate over the medium to long term.

The purpose of this project was to reassess a POS system that depended on legacy technologies and restructure it into a more maintainable and scalable platform to support store operations.

Specifically, the goal was to migrate to a new platform while fully understanding the existing functionality, maintain offline operations in stores, standardize integration with peripheral devices, and create an environment that makes it easier to add future features and respond to regulatory changes.

SMILE was responsible for analyzing the existing source code and documentation, organizing business workflows, designing the architecture, developing the POS application, redesigning the database, integrating peripheral devices, preparing the migration plan, and supporting regression testing and UAT preparation.

Rather than simply refreshing the screens, the reconstruction is being carried out based on a thorough understanding of legacy assets, while identifying differences between old and new functions and assessing the impact on store operations.

The key objective of this initiative was not simply to replace the POS with new technology, but to redesign the system architecture so it could accommodate future changes while maintaining the usability and stability required in store operations.

First, we organized the functions and data structure of the existing system, distinguishing between processes that were essential to store operations and those with room for improvement. Based on this analysis, we adopted React 18 for the front end and C# / ASP.NET Core .NET 8 for the back end, aiming to create a structure that makes functionality easier to understand and maintain.

Since store environments may also experience unstable network connectivity, the system is being designed on the assumption that offline operations must be maintained. By verifying the operation of essential in-store peripherals such as receipt printers, barcode readers, cash drawers, and payment terminals, we are bringing the system closer to the level of quality required for real-world use.

The main challenge was to interpret the existing VB6 / Access 2000-based system while gradually replacing it with a new technology stack. Because the existing processes contained years of accumulated business rules, simply recreating the interface could still have left practical differences in day-to-day operations.

In addition, it was essential that the POS remain usable even offline, and integration with peripheral devices used in stores was also critical. Implementation and verification had to proceed while confirming the control methods for each device and ensuring consistency with existing operations.

At SMILE, we are working in parallel to analyze current functions, identify business-level gaps, organize connection requirements for each peripheral device, and prepare regression test plans. Our goal is not simply to replace the system, but to modernize it with real-world operations in mind.

This project is expected to reduce maintenance risks caused by reliance on legacy technologies and establish a foundation that makes it easier to respond to future regulatory changes and functional improvements. In addition, redesigning the system around peripheral device integration and offline operation will help create a POS environment that store teams can continue to use reliably.

Another major benefit is that modernization can proceed while carrying forward knowledge from the existing system, making it easier to implement upgrades in phases while minimizing the impact on store operations.

For projects such as POS systems, where both business process understanding and device integration are critical, implementation skills alone are not enough. It is also essential to interpret the current specifications, align understanding among stakeholders, and define verification perspectives. At SMILE, the Japan and Vietnam teams work together to analyze the current system, confirm screen specifications, organize peripheral device requirements, and clarify testing perspectives.

This approach makes it easier to move development forward in stages, even in projects such as legacy modernization where there are many items to verify and decisions to clarify.

Modernizing a legacy POS requires more than migrating to new technologies; it also demands a clear understanding of existing business processes, continuity of store operations, and preservation of peripheral device integration. In this case study, we analyzed an existing POS based on VB6 / Access and rebuilt it on a new platform using .NET 8, React 18, and SQL Server, with the goal of balancing the stability needed to support store operations with the scalability required for future expansion.

For retailers considering the modernization of POS and store management systems, a phased renewal approach that starts with a clear understanding of existing assets can be an effective option.