Software design means two unrelated things depending on who is saying it. To a designer it is the interface. To an engineer it is the architecture: how the system is structured, where responsibilities sit and how components communicate. Agencies use the phrase loosely, and the mismatch is discovered after the contract is signed.
Establish which discipline is being sold
Ask directly whether the deliverable is interface design or a technical architecture, and who produces it. A firm answering with wireframes is selling the first. A firm answering with component boundaries, data flow and deployment topology is selling the second. Both are legitimate and they employ different people at different rates. The confusion is expensive because you can complete an engagement and still be missing the half you assumed was included.
What an architecture deliverable should contain
If you are buying system design, require something specific: the major components and their responsibilities, the data model, how components communicate and what happens when one is unavailable, where state lives, and the decisions that were considered and rejected with reasons. That last item is the most valuable and the most often omitted, because it is what lets a future team change the design without repeating the analysis.
Design without implementation responsibility drifts
An architecture produced by people who will not build it tends to be optimistic, and an interface designed by people who will not implement it tends to be expensive. Either way the correction happens silently under deadline. Require the designing party to review the implementation at least once, and require the implementing party to review the design before it is signed off. A single scheduled conversation prevents most of this.
Ask what the design assumes about scale and security
Designs are only valid within assumptions, so get them written down: expected volumes, acceptable latency, availability requirements and what data is sensitive. A system designed for thousands of records behaves differently at millions, and a design that did not know customer data was involved will not have separated it. The elements at 16 CFR 314.4 are a reasonable prompt for the security assumptions that should be explicit in any architecture.
Questions people ask about software design service
What does a software design service actually deliver?
Either interface design or system architecture, depending on who is selling. Ask directly: wireframes mean the first, component boundaries and data flow mean the second. They are different people at different rates and the confusion is expensive.
What should an architecture document contain?
Components and responsibilities, the data model, how components communicate and behave when one is unavailable, where state lives, and the options considered and rejected with reasons. The last is the most valuable and most often missing.
Can the designer be different from the builder?
Yes, if you force one conversation: the implementing party reviews the design before sign off, and the designing party reviews the implementation at least once. Without that, corrections happen silently under deadline.