Interview Questions for a Software Architect

Design a system for a high-write, read-heavy workload and walk me through your tradeoffs.

What to look for: Clarifies requirements and scale first, then reasons about storage selection, caching, read replicas, partitioning, and consistency. Names tradeoffs explicitly rather than presenting one fixed answer.

When would you choose a modular monolith over microservices, and what makes you reconsider?

What to look for: Considers team size, operational maturity, domain boundaries, and deployment needs. Avoids cargo-cult microservices, and recognizes the distributed-systems tax of network, consistency, and observability complexity.

How do you choose a consistency model for a feature spanning multiple services?

What to look for: Distinguishes strong from eventual consistency, discusses sagas, idempotency, and outbox patterns, and ties the choice to business tolerance for staleness. Concrete reasoning about failure modes.

Walk me through how you write an architecture decision record.

What to look for: Captures context, the decision, the alternatives considered, and the consequences and tradeoffs. Treats ADRs as durable reasoning others can revisit, not bureaucratic paperwork.

How do you fold non-functional requirements like scalability, security, reliability, and cost into a design?

What to look for: Quantifies targets such as latency, availability, and budget up front and designs to meet them, rather than bolting them on later. Makes cost and security first-class constraints.

How do you evaluate a new technology before recommending adoption?

What to look for: A scoped proof of concept against real requirements, with criteria, risks, and an exit plan. Weighs operational cost and team familiarity, not just technical novelty.

Tell me about a system you designed and evolved over time. What changed and why?

What to look for: A real production system, the original constraints, and how the architecture adapted to scale, new requirements, or debt. Shows ownership of evolution, not just greenfield design.

Describe an architectural decision you got wrong. How did you discover and correct it?

What to look for: Intellectual honesty, the signal that revealed the mistake, and a measured migration or reversal. Reflects on what they would document differently next time.

Tell me about a time you balanced delivery speed against long-term system health.

What to look for: A deliberate, documented tradeoff with a plan to repay debt, not an absolutist stance. Pragmatism that ships value while protecting the system.

Give an example of raising the design bar across a team or organization.

What to look for: Mentoring, design reviews, guardrails, or standards that improved others' work. Influence that scales beyond the architect's own keyboard.

A core service is hitting a scaling bottleneck under growth. How do you diagnose and address it?

What to look for: Measuring before changing, finding the true bottleneck across CPU, IO, locks, or downstream calls, and addressing it with the least invasive change. Avoids premature rewrites.

Two teams want incompatible integration patterns at a shared boundary. How do you resolve it?

What to look for: Defining a clear contract and integration standard, weighing each team's needs, and deciding with documented rationale. Aligns through reasoning and influence rather than mandate.

Leadership gives you a product strategy. How do you turn it into a technical roadmap?

What to look for: Translating business goals into capabilities, sequencing by risk and dependency, and identifying architectural investments needed to support the plan. Connects strategy to concrete technical bets.

You inherit a system with significant tech debt and active feature pressure. How do you proceed?

What to look for: Assessing risk and bottlenecks, prioritizing debt that blocks delivery or reliability, and interleaving paydown with features. A defensible plan, not a stop-the-world rewrite.

A vendor or third-party service you depend on becomes a single point of failure. How do you mitigate it?

What to look for: Assessing blast radius, adding redundancy, circuit breakers, graceful degradation, or an abstraction that allows swapping. Designs for failure of dependencies rather than assuming uptime.

How do you get buy-in for an architectural decision without positional authority?

What to look for: Clear written rationale, listening to objections, prototypes that de-risk, and bringing teams along. Influence through evidence and trust rather than mandate.

How do you run an effective architecture or design review?

What to look for: Reviewing against requirements and guardrails, asking probing questions, and leaving authors with actionable guidance. Raises quality without becoming a bottleneck or a gatekeeper.

How do you mentor engineers to think architecturally?

What to look for: Coaching on tradeoffs and system thinking, pairing on design, and giving ownership with guardrails. Scales judgment across the team rather than centralizing every decision.