India’s digital payments revolution — UPI, mobile banking, real-time settlements — runs on top of core banking systems that, in many cases, were designed before smartphones existed. The front end looks modern. The back end is struggling to keep up.

Core banking systems are the operational backbone of every bank. They process deposits, loans, account management, interest calculations, regulatory reporting, and interbank settlements. When a core banking system is slow, unreliable, or inflexible, every digital initiative built on top of it suffers.

For many Indian banks, especially in the public sector, that suffering is becoming impossible to ignore.

The Scale of the Problem

Most of India’s scheduled commercial banks run their core operations on one of three platforms: Infosys Finacle, TCS BaNCS, or Oracle Flexcube. These systems were originally deployed in the early 2000s during India’s first wave of banking computerisation under the RBI’s mandate.

They’ve served well. But they were designed for a different era — one where branch banking was primary, transaction volumes were a fraction of current levels, and real-time processing was a luxury rather than an expectation.

Today’s demands are fundamentally different. UPI alone processes over 15 billion transactions monthly. Banks are expected to offer real-time account updates, instant loan approvals, personalised product recommendations, and API-based integration with hundreds of fintech partners. The original architecture of these core systems wasn’t built for this volume or this complexity.

The result is visible in performance metrics. Several public sector banks report core system response times that degrade significantly during peak UPI transaction hours. Batch processing windows — originally designed for overnight reconciliation — are shrinking as 24/7 transaction volumes leave less and less idle time.

Why Banks Haven’t Upgraded Already

If the problem is clear, why haven’t banks solved it? Three factors explain the delay.

Risk. Replacing a core banking system is one of the highest-risk technology projects a bank can undertake. It touches every product, every process, and every customer. A botched migration can halt operations. The industry is littered with examples of core banking migrations that exceeded timelines by years and budgets by hundreds of crores. Nobody wants to be the next cautionary tale.

Cost. A full core banking replacement for a large public sector bank can cost Rs 1,500-3,000 crore when you include licencing, customisation, data migration, testing, training, and the inevitable overruns. For banks already under pressure to improve capital adequacy and reduce NPAs, this is difficult to justify.

Vendor lock-in. As discussed widely in the industry, decades of customisation and integration have created deep dependencies on existing vendors. The switching cost isn’t just the new system — it’s unwinding everything built around the old one.

The Modernisation Approaches

Banks that are moving forward are adopting different strategies depending on their starting position and risk appetite.

Incremental modernisation. Rather than replacing the core system wholesale, some banks are wrapping it with modern API layers and moving specific functions to newer platforms. A bank might keep its existing core for deposit management but deploy a modern cloud-native system for loan origination. This reduces risk but creates architectural complexity.

Progressive replacement. A few banks are pursuing a “strangle” strategy — building new functionality on a modern platform while gradually migrating existing functions away from the legacy core. This takes longer but allows parallel operation and phased risk management.

Full replacement. Some smaller banks and newer entrants are opting for clean-slate implementations on cloud-native core banking platforms. Companies like Thought Machine, Temenos (with its cloud-native offering), and India’s own Nuclei are pitching modern alternatives designed for API-first, real-time operations. Banks exploring this route often engage AI implementation help to ensure they’re building the right technical architecture from the start.

What the RBI Expects

The RBI hasn’t mandated specific core banking platforms, but its direction is clear. The 2025 IT governance guidelines emphasise:

• Real-time transaction processing capability as a baseline expectation
• API readiness for Account Aggregator and ONDC integration
• Cyber resilience standards that legacy systems struggle to meet
• Cloud adoption frameworks that require modern architectural foundations

Banks that delay core modernisation will increasingly find themselves unable to comply with regulatory expectations, not because of any single mandate, but because the cumulative demands assume modern infrastructure.

The Public Sector Challenge

Private sector banks and new-generation small finance banks generally have more flexibility to modernise. They’re smaller, less encumbered by legacy customisation, and more willing to invest in technology.

Public sector banks face a harder path. They’re larger, more heavily customised, and subject to procurement processes that slow technology decisions. Their IT teams are often understaffed relative to the complexity they manage.

The government’s push to improve public sector bank technology through recapitalisation and digital mandates helps, but money alone doesn’t solve the problem. These are fundamentally organisational challenges — getting thousands of employees trained on new systems, migrating billions of records without errors, and maintaining service continuity throughout.

The Cost of Waiting

The counterargument to delay is that waiting makes the problem worse. Every month of continued operation on an aging core system adds more data, more customisations, and more dependencies that make eventual migration harder.

Banks that modernise now will be positioned to offer the products and services that India’s digital economy demands. Banks that wait will find themselves unable to keep up with UPI’s expanding functionality, the Account Aggregator ecosystem, ONDC integration, and whatever comes next.

The core banking upgrade isn’t optional anymore. It’s a question of timing and approach. Banks that plan proactively, manage risk carefully, and invest adequately will come through it stronger. Those that treat it as a problem for tomorrow will find that tomorrow arrives faster than expected.