Containerised, portable, anywhere you can run containers.

The decision is rarely technical, and it's useful to recognise that immediately.

European cloud is the default where there are no particular constraints: it costs less to run, elasticity is immediate and it doesn't tie up your infrastructure team. It suits most projects, including many applications handling ordinary personal data.

On-premise becomes the choice where contractual or regulatory data residency constraints exist, where integration with systems that never leave the corporate network would otherwise be awkward, or where an infrastructure team already exists and prefers to keep everything in-house. It's frequent in healthcare, public sector, finance and utilities.

Hybrid is often the best compromise where a customer- or citizen-facing portal exists: the public part on cloud, the application core and sensitive data on site, with a controlled channel between them.

What to verify during evaluation is that the choice stays reversible, because constraints change. Here it is, because there are no dependencies on one provider's managed services.

A serious project has at least two environments: one in production and one where changes are verified before being applied. It sounds obvious and in practice it's where many projects economise, with predictable consequences.

Because every project is an isolated environment with its own network, volumes and ports, creating a second environment is an ordinary operation, not a parallel infrastructure to design. The configuration describing the domain is versioned like any document, so promoting a change from the verification environment to production is a controlled step and not a manual intervention.

Where data separation is a requirement, the verification environment works on anonymised or synthetic data: that too is a choice to make deliberately at the start, because building a usable test dataset afterwards is harder than it sounds.