Dev Skill Programme
Developer A

Developer A · Backend

Database and API: data modelling, SQL, indexes and transactions, plus API design, auth, validation, errors, versioning and operations.

Skill page

Verified level

AAdvanced★High confidence

Reviewed 2 months ago by Developer B.

Self assessment

AAdvanced

At or below the verified level.

Target

AA

Target met.

Checklist

0/29

Nothing flagged.

Assessment history (2)

  1. Verified gradeAAdvancedQ&A 92.5%High confidence25 Aug 2026

    Confirmed at this level against the evidence on file.

    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
    • CorrectHow do you run a schema migration on a large live table without downtime? · Database · Advanced 3pt
    • CorrectHow would you ship a breaking change to an API that mobile apps already use? · API · Advanced 3pt
    • CorrectHow 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

    • KnowledgeA
    • ImplementationA
    • Code UnderstandingA
    • DebuggingA
    • DesignA
    • CommunicationA

    Independence from AI

    Can explain AI-generated codeYes
    Can modify AI-generated codeYes
    Can identify incorrect AI-generated codeYes
    Can debug without AIYes
    Can make technical decisions without blindly following AIYes

    Understands and controls the solution (100%).

    Evidence cited (5)

    • Architecture explanation
    • Debugging task
    • Code review
    • Real project contribution
    • Knowledge questions

    Assessor: Developer B· Skill owner review

  2. Self assessmentAAdvanced20 Aug 2026

    Primary skill — day-to-day work in this area.

    Dimensions

    • KnowledgeA
    • ImplementationA
    • Code UnderstandingA
    • DebuggingA
    • DesignA
    • CommunicationA

    Recorded by the member· Self assessment

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