CTO Systems Architecture & Infrastructure 4

Question 1

A CTO must architect a real-time bidding platform that requires sub-5ms p99 response times at 1 million requests per second. Which infrastructure decision has the highest impact on meeting this SLA?

Accepted Answer

Deploying in-process caching with pre-warmed data and co-locating compute near network edge

Answer

Sub-5ms p99 at scale requires eliminating network round trips to external stores; in-process caches and edge co-location are the dominant latency levers.

Question 2

Which load balancing algorithm is most appropriate for backend services where request processing time varies significantly (e.g., some requests take 1ms, others 500ms)?

Accepted Answer

Least connections (or least outstanding requests)

Answer

Least-connections routes new requests to the server with the fewest active connections, naturally avoiding hot spots caused by slow requests holding connections.

Question 3

When implementing zero-downtime schema migrations for a high-traffic relational database, which technique avoids locking the table during an ALTER operation?

Accepted Answer

Using an online schema change tool (e.g., pt-online-schema-change, gh-ost) that operates on a shadow copy

Answer

Online schema change tools copy data to a shadow table while applying live writes via triggers, then atomically swap the tables without long locks.

Question 4

A CTO is evaluating a content delivery network strategy. Which caching behavior represents a security risk for authenticated API responses?

Accepted Answer

Caching responses that include Set-Cookie or user-specific data without Vary: Cookie headers

Answer

Without a Vary: Cookie header, CDN edge nodes may serve one user's authenticated response to another user, leaking sensitive data.

Question 5

An engineering team debates between synchronous REST and asynchronous event-driven messaging for inter-service communication. In which scenario does asynchronous messaging provide the clearest architectural advantage?

Accepted Answer

An order placed event that triggers inventory reservation, fraud check, and email notification concurrently

Answer

Asynchronous messaging enables fan-out to multiple consumers in parallel without the caller waiting, which is ideal for multi-step post-order processing.

(CTO) Certified Chief Technology Officer Practice Test

(CTO) Certified Chief Technology Officer Practice Test

CTO Systems Architecture & Infrastructure 4