Enterprise Architecture principles
5. Cloud first
- Last reviewed
- 8 June 2026
- Owner
- Head of Architecture
Rent, before buy, before build. Do not build what can easily be bought off-the-shelf. Prioritise cloud-based services over on-premises alternatives.
Rationale
Commercial-off-the-shelf (COTS) services include the cost of development, operation and best practice in their costs, and share these between all clients. Total Cost of Ownership (TCO) is cheaper for ‘utility’ functionality.
Leverage scalability, cost-effectiveness and agility of cloud services.
Implications
Conduct an options appraisal before choosing a delivery approach.
Evaluate COTS solutions against what’s “good enough”, as they are unlikely to meet all requirements - they may need façades, configuration or a hybrid approach to meet user needs. For example, if a COTS solution delivers 80% of user needs, consider wrapping or extending the COTS solution for the remaining 20%, rather than building 100% bespoke.
Avoid customisation of COTS solutions to deliver bespoke functionality. Where required, use configuration and integration to tailor the solution to user needs. Adapt business processes to align with COTS where possible.
Develop an exit strategy before adopting COTS, to prevent vendor lock-in.
Evaluate TCO between COTS and bespoke options during options appraisal. This should include hosting, platform, delivery resource and support costs, for the lifetime of the product.
Prioritise Software-as-a-Service (SaaS) services, over Platform-as-a-Service (PaaS), over Infrastructure-as-a-Service (IaaS), over on-premises options, when evaluating service hosting options.