Developer C · Backend

1. Verified gradeCWorkingQ&A 73.8%Medium confidence25 Aug 2026

   Good grasp of the concepts, and explains the happy path well. Could not yet talk through the failure modes without help.

   Q&A — 20 questions

   • CorrectWhat is the difference between a primary key and a foreign key? · Database · Basic 1pt
   • CorrectExplain one-to-many and many-to-many relationships, and how each is stored. · Database · Basic 1pt
   • CorrectWhat does NULL mean in SQL, and why does `WHERE col = NULL` not work? · Database · Basic 1pt
   • CorrectWhat are the common HTTP methods and what is each used for in a REST API? · API · Basic 1pt
   • CorrectWhat do the status code families mean? Give an example of each: 2xx, 4xx, 5xx. · API · Basic 1pt
   • CorrectWhat is the difference between authentication and authorization? · API · Basic 1pt
   • CorrectWhat is the difference between INNER JOIN and LEFT JOIN? When would you use a LEFT JOIN? · Database · Intermediate 2pt
   • CorrectWhat is the difference between WHERE and HAVING? · Database · Intermediate 2pt
   • CorrectWhat is an index, what does it cost, and when should you add one? · Database · Intermediate 2pt
   • CorrectWhat is a transaction, and what does ACID stand for? · Database · Intermediate 2pt
   • CorrectWhat does idempotent mean? Which HTTP methods are idempotent? · API · Intermediate 2pt
   • CorrectWhere should input validation happen, and what should the API return for invalid input? · API · Intermediate 2pt
   • CorrectHow does token-based authentication with a JWT work, and where are its weaknesses? · API · Intermediate 2pt
   • CorrectCompare offset pagination with cursor pagination. · API · Intermediate 2pt
   • CorrectExplain transaction isolation levels and one anomaly that READ COMMITTED allows. · Database · Advanced 3pt
   • CorrectA report query became slow in production. How do you investigate and fix it? · Database · Advanced 3pt
   • PartialHow do you run a schema migration on a large live table without downtime? · Database · Advanced 3pt
   • WrongHow would you ship a breaking change to an API that mobile apps already use? · API · Advanced 3pt
   • WrongHow do you protect an API against abuse or traffic spikes? · API · Advanced 3pt
   • WrongA request is slow only sometimes in production. How do you find the cause? · API · Advanced 3pt

   Dimensions

   • KnowledgeB
   • ImplementationC
   • Code UnderstandingC
   • DebuggingD
   • DesignD
   • CommunicationC

   Independence from AI

   Can explain AI-generated codeYes

   Can modify AI-generated codeYes

   Can identify incorrect AI-generated codePartly

   Can debug without AIPartly

   Can make technical decisions without blindly following AIPartly

   Mostly in control, some reliance (70%).

   Evidence cited (2)

   • Practical task
   • Knowledge questions

   Weak areas

   Indexes, transaction isolation and authorization edge cases.

   Recommended learning

   Read a query plan for a slow report and add an index; then implement an endpoint with ownership checks.

   Assessor: Developer B· Skill owner review·Database Fundamentals· next assessment 28 Dec 2026

2. Self assessmentBProficient20 Aug 2026

   Completed the concept session and the first block of the checklist.

   Dimensions

   • KnowledgeA
   • ImplementationB
   • Code UnderstandingB
   • DebuggingC
   • DesignC
   • CommunicationB

   Recorded by the member· Self assessment

Append-only — a new assessment never overwrites an old one.