modernizing a critical system to unlock scale, stability, and new business value

Localiza

Legacy System Modernization

Microservices & API Development

Cloud-Native Architecture & Scalability

Digital Product Integration

Test Automation & Quality Assurance

Legacy systems often hold businesses back from their full potential. They become increasingly complex over time, difficult to maintain, and create bottlenecks for innovation. When these systems are at the core of a company’s operations, the challenge of modernizing them becomes both critical and delicate, requiring surgical precision to transform without disrupting the business.

Founded in 1973, Localiza is the largest car rental company in Latin America and one of the largest in the world, with operations in Brazil, Argentina, Colombia, Chile, Ecuador, Paraguay, and Uruguay. The company maintains a fleet of over 300,000 vehicles and serves millions of customers through more than 500 corporate and franchised branches. With a focus on continuous innovation and exceptional customer experience, Localiza has maintained its market leadership for nearly five decades.

monthly requests

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What we set out to do

Bring scalability, resilience, and integration capabilities to a business-critical system — all while it remained operational.

The Contract Management System (GC) lies at the heart of Localiza’s operations, supporting every rental transaction across the organization. Originally built as a monolithic solution with over 1.2 million lines of code, GC’s legacy architecture presented numerous challenges: limited scalability, downtime during deployments, poor API governance, and dependency on aging .NET technologies.

As customer expectations evolved and operational complexity increased, the need for a digital transformation became undeniable. The challenge was to break apart and modernize a complex, high-risk system, without interrupting business operations, while simultaneously enabling new strategic initiatives across the company.

The goal was to stop the expansion of the legacy monolith and progressively replace it with a modular, modern solution. A phased strategy was implemented to decompose the system’s business areas into independent modules, eventually replacing them with isolated microservices. This approach allowed the team to build for the future while still maintaining critical day-to-day operations.

Opportunity

Create a flexible architecture that supports integration with new products and unlocks value, even mid-transformation.

lines of code refactored

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A key challenge in any system modernization is delivering business value throughout the process, not just at its conclusion. The team solved this by introducing a new REST API communication layer within the legacy system, acting as a bridge between old and new components. This allowed the business to connect new digital products and services even while the modernization was still in progress.

The strategy paid dividends quickly, enabling several key integrations:

New internal mobile applications that interact with contract data in real time, giving agents the flexibility to serve customers anywhere in the rental location.
A completely redesigned invoice issuing process for contracts, streamlining financial operations and reducing manual work.
Partnership integrations with external companies — including ride-hailing platforms, insurance providers, and toll & parking services via vehicle tags.

These integrations proved that the architectural evolution was not only technical but also strategic, unlocking new revenue streams and digital customer experiences mid-transformation. The modular approach allowed the team to prioritize high-value business domains for extraction first, delivering immediate benefits rather than waiting for the entire system to be modernized.

monthly requests handled by the legacy monolith alone

0 M

Value Delivered

The modernized architecture supports 13 integrated systems, 12 REST APIs, and over 60 satellite applications, with 42 processors managing operations, 18 batch routines, and 1,268 automated test scenarios ensuring consistency and stability.

The new architecture greatly improved scalability, resilience, and cost-efficiency. Components now scale independently, avoiding system-wide failures. Developer teams gained autonomy, accelerating delivery and reducing reliance on a central team.

Security also improved with better isolation and more transparent access controls. Granular, service-level monitoring replaced the limited visibility of the old monolith.

The modernization of GC has delivered strong results across the business. Maintenance costs are down, scalability and system resilience have improved, and security risks have been reduced through component isolation. Developer autonomy has increased, and the system now supports fast, flexible integration with new tools and partners.

By modernizing GC with precision, Localiza turned a critical legacy system into a foundation for ongoing innovation, transforming it from a bottleneck into a driver of digital growth.