Computer Science Level 3 case studies
Computer Science Level 3 · Put your knowledge to work in context.
Computer Science Level 3 is a mid-tier credential for people who can already write working programs and now need to reason about them formally. Candidates typically include second- or third-year computing students, career changers who have finished an introductory programming sequence, and working developers filling gaps in algorithms or systems knowledge. The exam is split into six weighted domains: computational thinking and algorithms, programming and software development, data structures and data management, computer systems, networks and security, data analysis and computational applications, and the impacts of computing and professional practice. Expect a mix of multiple-choice items testing precise definitions and trace-through reasoning, plus constructed-response tasks where you write pseudocode, justify a complexity claim, or explain a design trade-off. The Computer Science Level 3 case studies are 5 cases and about 3,334 words.
1The Overtime Scheduling Bug
A hospital's shift-scheduling tool assigns nurses to 4-hour blocks. The team wrote a greedy routine: sort nurses by fewest assigned hours, then for each block assign the first nurse who is free and has not exceeded 36 hours this week.
631 words, about 3 min2The Intermittent Checkout Outage
An online store's checkout service calls a payment provider over HTTPS. Roughly 0.4% of checkouts fail with a 30-second timeout, clustered in bursts of a few minutes, mostly at peak traffic.
668 words, about 3 min3The Duplicate-Key Cache
A service stores user profiles in a hash map keyed by user ID, with a least-recently-used eviction policy capped at 10,000 entries. It also keeps a separate sorted list of user IDs for range queries.
734 words, about 4 min4The Slow Dashboard Query
A school district dashboard shows average test scores by school and grade. The source table has 4 million rows: one per student per test, with columns student id, school id, grade, subject, score, and test date.
681 words, about 3 min5The Automated Grading Tool
A coding bootcamp deploys an automated grader that runs student-submitted code in containers and scores it against hidden tests. Submissions run as root inside the container, which has network access and mounts a shared volume for reading test files.
620 words, about 3 min