Enterprise engineering.

Run discovery on site with the people who will use the system, and turn what you see into a data model and service boundaries.

Build the services and interfaces in two to four week increments, each one demonstrated and accepted before the next.

Integrate with the third parties a client already depends on, to the point where the integration holds against their real behaviour.

Stay on the engagement after go-live and fix the causes of what goes wrong, not just the symptoms.

Several years building services or interfaces that other people depend on daily.

Depth in one server-side language and a relational database, or one modern front end framework, and comfort reading the other side.

Judgement about when to keep something simple and when the complexity is genuinely needed.

Clear written English, since most of the work is agreeing behaviour in writing before it is built.