Organisational Readiness
Whether an organisation has the skills, capacity, structure and appetite to operate a proposed architecture, independent of the design's technical merit.
The best architecture the organisation can actually run beats the better architecture it cannot. This is the constraint most often ignored in design, and the most reliable predictor of whether a design survives contact with production.
The dimensions to assess honestly:
Skills. Not whether the technology is learnable, but whether the team will have become competent by the time it is in production, and whether the market allows replacing the person who knows it.
Operational capacity. A design requiring a platform team to own it needs a platform team that exists and is funded. A mesh, a multi-region topology or a self-managed data store without an owner becomes a liability.
Structure. Conway's Law is not advisory. An architecture requiring capability-aligned teams will not be achieved by a functionally-siloed organisation, whatever the diagram says.
Change appetite and history. An organisation that has abandoned its last two modernisation programmes will abandon the third unless something structural changed.
The professional response is not to design for the ideal and hope. It is to design for the organisation as it is, and to state explicitly which capability investments would unlock a better design — making the constraint a funded decision rather than a silent failure.