Legacy IT infrastructure remains the backbone of many organisations, supporting critical operations, regulatory obligations and long established business workflows. The issue is not legacy technology itself, but the growing technical and organisational debt that builds up when it is poorly managed. Left unchecked, this debt drives rising energy consumption, deepens skills shortages and hardens inefficient ways of working, ultimately constraining both sustainability and change.
This challenge has become strategic, not just technical. DXC Technology’s global survey of 750 C-suite IT executives shows that 99 percent of organisations now track technical debt on their risk registers, while 46 percent say it directly limits their ability to pursue digital initiatives.
As Max Hemingway (CITP FBCS) at DXC Technology argues, organisations do not need to rip and replace legacy systems to succeed. They need to manage legacy deliberately – applying best practices that reduce debt, improve efficiency and sustainability, and ensure older platforms remain fit for the future while continuing to deliver business value.
What is organisational debt?
Organisational Debt extends far beyond technical debt and represents the accumulated capability gaps across infrastructure, applications, data, user experience (UX), processes and knowledge that limit an organisation’s ability to adapt and modernise.
As organisational debt grows through years of sub optimal trade-offs, workarounds, outdated hosting/storage platforms, diminishing skills and rigid processes it ultimately reduces flexibility, resilience and strategic agility.
The sustainability and efficiency connection
Efficiency and sustainability are intrinsically linked. In practice, the most sustainable IT environments are also the most efficient ones: systems that consume fewer compute resources, require less manual intervention and eliminate duplication inherently use less energy and generate fewer emissions. Inefficient architectures – characterised by over provisioning, redundant applications, complex integrations and manual operations – drive unnecessary energy consumption and operational waste, increasing both cost and environmental impact. By contrast, simplifying and rationalising technology estates improves performance, resilience and cost control while simultaneously reducing power usage and carbon footprint. Viewed through this lens, sustainability is not an additional constraint on IT decision making, but a natural outcome of well designed, well governed and efficient systems.
Best practices for sustainable, efficient legacy IT management
1. Recognise and quantify technical & organisational debt
Understanding and controlling legacy sprawl requires acknowledgement that both technical and organisational debt accrue interest over time. Debt can manifest over time with outdated systems, inefficient processes and legacy code that impede innovation and adaptability. Resulting in reduced organisational flexibility, resilience and strategic agility as the burden grows over time and increasing costs.
Recognising debt requires the Enterprise Architecture (EA) of your organisation is up to date and if necessary, a full estate discovery (including all aspects of organisational debt) should be carried out. Governance boards should be reviewed to ensure they are operating efficiently, capturing where decisions and approvals contribute to organisational drag.
DXC data shows organisations that tackle technical debt can achieve up to ~39 percent cost savings and retire about 37 percent of redundant applications – underscoring the financial and strategic impact of debt reduction.
2. Apply data-driven decision making
Successful migration programmes typically rely on data-driven runbooks, dependency mapping and quantitative analysis to guide decision making. Utilising data from EA, telemetry, performance analytics, emissions calculators and cost models can provide and drive the modernisation priorities.
3. Modernise strategically, phased and not Big Bang
Modernisation is a key strategy to removing debt but not everything should or can be replaced at once. Addressing debt through priority identification, selective modernisation and retirement actions can prove effective in reducing maintenance, cost and risk while increasing organisational agility and future transformation readiness.
Modernisation should be based on business / value impact, risk reduction and sustainability gains (lower carbon emissions and simpler rationalised estates), rather than being based solely on technology age. Utilise a phased replacement, agile approach and continuous improvement cycles to maintain stability and drive improvements.
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Successful modernisation programmes are not purely technical, but align to strategic business outcomes, faster time to market, better customer experience, transformation goals and improved organisational agility. Ultimately reducing organisational debt and improving competitiveness.
4. Automate legacy operations to improve efficiency
Automation can be applied in many different forms from scripting to Artificial Intelligence. Prioritisation of an automation first approach should be implemented to maximise legacy systems reliability. Automating monitoring, patching, configuration drift correction and routine maintenance can increase performance, security and uptime.
5. Embedding sustainability into technology decisions
Sustainable IT is increasingly linked to Environmental, Social and Governance (ESG) outcomes as older technologies often require more energy and generate higher emissions, especially legacy data centres compared to cloud environments powered by renewables. Modern technology can improve employee experience and morale, whilst up to date systems strengthen security and compliance capabilities.
Evaluating sustainability impacts alongside cost and performance allow the integration of ESG metrics into architectural reviews and technology investment cases. Consolidating and rationalising applications allows the elimination of unused or low value services and through the utilisations of GreenOps and green development practices.
6. Design for interoperability and composability
Modernisation does not always require full replacements. Composability can extend the life of legacy systems through the implementation of API layers and modular architectures to extract value and lengthen the life of the system. Technologies can allow the containerisation of some legacy applications on modern platforms and Operating Systems (OS) where retiring the platform is not an option.
7. Strengthen cybersecurity and compliance, addressing legacy weak points
Legacy platforms often heighten security risks and vulnerabilities due to outdated OS versions, unsupported software and fragile integration layers. Utilising the full EA data across the estate can help identify wider security risks, not just at a system and application layer. Upgrades and patching should be prioritised and automated with older systems undergoing levels of isolation, segmentation and compensating controls to maintain compliance and reduce threat exposure. Security can be improved by adopting a Secure by Design and zero-trust architecture posture.
8. Mitigate skill shortages proactively
One major element of organisational debt is workforce dependency on hard to-maintain legacy technologies due to challenges including scarcity of skilled resources, aging workforce and shadow IT building workarounds due to slow IT responsiveness.
Partnering with specialist companies, vendors and academia can reduce this risk and bring experience, skills, reusable reference architectures and patterns, reducing time to modernise. This provides opportunity for cross-training of internal teams and upskilling to meet the complexity of today’s platforms.
Conclusion
Achieving sustainable and efficient outcomes from legacy IT requires a balanced approach. One that recognises the weight of technical and organisational debt while building toward a modern, secure, efficient and environmentally responsible future.
