Banks are not only asking whether legacy systems still work. They are asking whether those systems can still support the cost, talent, agility, scalability, and AI-readiness expectations of modern banking.

The AWS-Sunline Executive Roundtable brought together banking leaders for a practical discussion on core modernization, risk, and operational continuity. A clear theme emerged: legacy core systems are becoming harder to sustain, not because they have stopped working, but because the environment around them has changed.

Banks described a set of connected pressures: difficulty finding new talent to support legacy systems, high maintenance cost, slower product launch cycles, and scalability constraints. These challenges are pushing modernization from a technology discussion into a business resilience agenda.

Sunline's Charley and Sutee joined the discussion to connect these market concerns with practical modernization experience. Charley framed the structural challenges and shared how progressive modernization can match different bank contexts. Sutee shared field lessons from Thailand, especially around coexistence, data transformation, and execution discipline.

What Banks Emphasized

Figure 1. The major legacy-core pressure points highlighted by banks during the roundtable.

Talent continuity

Many banks highlighted the growing challenge of legacy talent. Legacy systems still support mission-critical banking operations, but the people who know how to maintain and enhance these systems are retiring, moving on, or becoming harder to replace. At the same time, newer technology talent is less likely to build careers around older platforms. This creates a talent continuity risk for banks that still depend heavily on legacy core environments.

Cost pressure

Cost was another major concern. Legacy and proprietary systems remain expensive to operate and maintain. As banks face increasing pressure to improve efficiency, reduce long-term technology cost, and invest in digital growth, the economics of legacy infrastructure are becoming harder to justify.

Agility and scalability

Banks also emphasized agility and scalability. Financial institutions need to launch products faster, respond to customer needs more quickly, and support new digital channels and ecosystem partnerships. Legacy cores often make this difficult. Product changes can take longer than the business expects, integrations can become complex, and scaling for new growth models can require significant effort.

These pain points are also contributing to broader commoditization pressure in banking. As products and services become easier for customers to compare, banks need to differentiate through speed, experience, personalization, and continuous innovation. That is difficult when the core system limits how fast the bank can change.

Sunline Perspective from Charley

During the discussion, Charley from Sunline echoed the banks' concerns and shared Sunline's perspective on the structural challenges facing banks. Cost, talent, agility, and scalability are not separate issues. They are connected symptoms of a deeper modernization challenge.

Many legacy core environments were designed for stability and control, which remain essential. But banks now need stability together with the ability to change continuously. This is why modernization must be assessed not only as a system replacement decision, but also as a long-term change-capability decision.

Charley's perspective: 

Modernization is not one model for every institution. The right approach depends on the bank's size, complexity, risk appetite, and business priorities.

Progressive Modernization and Coexistence

Charley also shared how a progressive modernization approach can help banks manage these challenges. Rather than forcing every institution into a single transformation model, Charley emphasized that banks can adopt different modernization methodologies depending on their context. Some banks may choose a more direct replacement approach, while others may need a phased coexistence model, where capabilities move progressively from the legacy core to the modern platform.

Figure 2. A progressive modernization model can reduce risk while allowing banks to move at a practical pace.

The roundtable also moved into one of the most important modernization questions: how can banks transform without creating unnecessary risk? Several banks raised concerns about coexistence. Running a legacy core and a modern core at the same time is not simple. It requires clear architecture, strong integration, reliable data synchronization, disciplined reconciliation, and careful operational governance.

Data transformation was another important topic. Banks want to modernize in a way that minimizes risk and protects business continuity. That means data migration cannot be treated as a one-time technical exercise. It must include mapping, cleansing, validation, reconciliation, cutover planning, and rollback readiness. The goal is not only to move data, but to prove that the migrated data is complete, accurate, usable, and trusted.

Practical Lessons from Sutee and the Thailand Market

Sutee from Sunline shared practical experience from the Thailand market, where core modernization has required careful planning, strong coexistence management, and close attention to migration risk. These experiences reinforced an important lesson: successful modernization depends not only on technology, but also on execution discipline.

Banks need a clear roadmap, realistic migration stages, strong data governance, and business validation at every major step. Coexistence is not simply a temporary technical bridge. It must be actively governed so that customer impact, operational ownership, data consistency, and business controls remain clear throughout the transition.

AI Readiness Depends on Core and Data Foundations

AI was another forward-looking theme from the roundtable. Many banks are exploring how AI can improve productivity, business intelligence, and decision-making. But the discussion also made clear that AI readiness depends on the strength of the underlying core and data foundation.

AI can create value when it works with trusted data, clear governance, and reliable systems of record. Without that foundation, AI may increase complexity rather than reduce it. For banks, this means core modernization and data modernization are closely linked to the future role of AI in productivity, customer insight, and business intelligence.

Closing Takeaway

The key takeaway from the roundtable is that core modernization is no longer just an IT agenda. It is a business resilience agenda. It is about reducing dependence on scarce legacy skills, lowering long-term cost, improving speed to market, supporting future scalability, enabling AI readiness, and giving banks the ability to change safely.

For banks, the path forward does not need to be disruptive. Modernization can be progressive. Coexistence can be managed. Data migration can be controlled. Risk can be reduced through proven methodology, clear governance, and practical market experience.

The discussion confirmed what many banking leaders already recognize: the future of core banking is not only about replacing old systems. It is about building the capability to evolve continuously, confidently, and at the pace the market now demands.