Cloud Architect interview questionsDesign review — the account structure decision round

Purpose

Puts the candidate in the reviewer's seat with a deadline, so the review has consequences and a vague "looks reasonable, a few thoughts" is visibly not enough.

Purpose

The load-bearing question. Anyone can say "account per team"; the separator is whether the candidate tests the record's reasoning against its own context — would this decision have stopped June? — and recognises a decision that is expensive to reverse being presented as cheap.

Signals to score

• Tests the decision against its own context, and shows that a role-name prefix and tag scoping would not have stopped a script run under a broad administrator role
• Calls "a permissions issue" a description that hides what happened, and restates the context in plain terms
• Rejects "easy to revisit later": moving live queues, databases, networks and storage between accounts means recreating them
• Notes that the options section has one dismissed alternative and no numbers, and names the options a reader would expect to see weighed
• Notes that the consequences list only benefits, and names at least two costs of the decision as written
• Separates the account structure and central egress into two decisions with different owners and different costs of reversal
• Notices that the status says Accepted before review, with no owner and no date or trigger for revisiting it
• Says that tag-based access depends on tags finance calls incomplete, on who may change a tag, and on services that honour tag conditions at all
• Names what should survive any rewrite: single sign-on with short-lived credentials, no long-lived keys, an audit trail nobody can switch off

Follow-up questions

• Would anything in this decision have stopped what happened in June?
• The last line says this is easy to revisit later. Is it?
• What options would you expect to see weighed, and which numbers would decide between them?
• Why might this be two decisions rather than one?
• What in the record would you keep word for word?

Purpose

Moves from critique to design, so a candidate who is sharp at finding faults has to show the structure they would stand behind.

Purpose

Tests whether the candidate draws boundaries that limit blast radius by construction rather than by convention, and prices the structure honestly for the people inside it.

Signals to score

• Makes the account — or subscription, or project — the unit that limits blast radius, with at least one production account per team
• Keeps shared foundations in their own accounts — network, audit logs, security tooling, backups — with narrower access than any team's account
• Puts guardrails at the organisation level that no account can switch off, and names two or three concretely
• Keeps identity central: one single sign-on, team access to team accounts, and emergency access held separately and alarmed when used
• Automates creating an account with a baseline — network attachment, logging, guardrails — so the overhead is paid once by the platform rather than by each team
• Gives every account its network ranges from one address plan, so accounts can be connected later without renumbering
• Says how one team reaches another team's queue or storage when it genuinely needs to, and who approves it
• Plans the way out of the shared production account: new services start in team accounts, billing moves first because it asked, the rest move by a stated date
• Names what the structure costs the teams — more places to look, cross-account access to set up, per-account quotas — without pretending it is free

Follow-up questions

• In your structure, what stops the data team's script?
• A team needs a new production account. Who creates it, and how long does it take?
• The data team legitimately reads billing's events. How does that work in your design?
• What does this cost the fourteen teams that the current structure does not?
• Everything is in one production account today. What moves first, and what may never move?

Purpose

Tests whether the candidate finds the concern behind a demand, says no to the right part of it in words the person can accept, and knows who must agree before a record changes status.

Signals to score

• Finds the concern behind the security lead's demand — data leaving for storage the organisation does not own — and meets it with a private route and a policy that allows only the organisation's own buckets
• Asks for the firewall's price and the storage volume, and works out the security lead's version: about 60 TB at $0.065 per GB, roughly $3,900 a month, plus a firewall in the path of every storage call
• Accepts the billing lead's request for their own production account, and declines "run it ourselves" in favour of the same baseline every account gets
• Accepts the finance partner's need and says that accounts give cost per team even when tags are incomplete
• Answers the naming comment in a sentence and moves on
• Decides who must agree before the record returns to Accepted and who only needs to be told
• Says what they would tell each person directly, before replying in the thread, where the answer is no
• Changes the record where a comment was right, and says in the record which comment changed it

Follow-up questions

• What is the security lead actually worried about?
• The billing team says they will run their own account if they have to. What do you say?
• Finance says tags have never been complete. Does your structure need them to be?
• Which of these do you answer in the thread, and which person do you talk to first?
• Who has to agree before this record is Accepted again?

Purpose

Tests whether getting a decision through the people it affects is something the candidate has done, with a real cost and a real refusal, rather than something they can describe well about a pack.

Signals to score

• Describes a specific decision, roughly when it was made, and who it affected
• States the objections in the objectors' own terms, not as resistance to be overcome
• Names something they changed because of an objection, and why the objection was right
• Names something they refused to change, and how the person heard about it
• Says whether the decision was written down, and what the record said about options and consequences
• Says how it turned out, including anything they would now do differently
• Keeps the story on the decision and its reasons rather than on the politics around it

Follow-up questions

• In their own words, what did the people who objected want?
• What did you change because of them?
• What did you refuse to change, and how did they find out?
• Looking back, who was right?

Purpose

A candidate who has lived with decisions asks who owns them and whether they get revisited; one who has not asks about the template. The topics offered make the choice the signal.

Purpose

A specific, unflattering fact shows the candidate this round wants what the work is, and discourages one who expects the foundations to be settled. Say it only while it is true.