Dev Skill Programme
Developer D

Developer D · Backend

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

Skill pageAssess

Verified level

DFundamentalLow confidence

Reviewed 2 months ago by Developer B.

Self assessment

DFundamental

At or below the verified level.

Target

DC

1 level(s) to go.

Checklist

0/29

Nothing flagged.

Assigned to reach C by 13 Oct 2026 — Focus on tables, keys and relationships first.

Assessment history (2)

  1. Verified gradeDFundamentalQ&A 62.5%Low 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
    • WrongA report query became slow in production. How do you investigate and fix it? · Database · Advanced 3pt
    • WrongHow 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

    • KnowledgeC
    • ImplementationD
    • Code UnderstandingD
    • DebuggingE
    • DesignE
    • CommunicationD

    Independence from AI

    Can explain AI-generated codePartly
    Can modify AI-generated codePartly
    Can identify incorrect AI-generated codeNo
    Can debug without AINo
    Can make technical decisions without blindly following AINo

    Largely dependent on AI output (20%).

    Evidence cited (1)

    • Knowledge questions

    Assessor: Developer B· Skill owner review· next assessment 29 Oct 2026

  2. Self assessmentDFundamental20 Aug 2026

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

    Dimensions

    • KnowledgeC
    • ImplementationD
    • Code UnderstandingD
    • DebuggingE
    • DesignE
    • CommunicationD

    Recorded by the member· Self assessment

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