Backend development

Stage 1 · Lesson 7 of 10

DNS: from a name to an address

Your language and how HTTP works

Computers find each other by number (an ), but people use names like api.example.com. , the Domain Name System, is the phone book that turns the name into the number. The client asks a resolver, a helper server that does the lookup for it.

The resolver asks the root servers, then the .com servers, then the domain's own name servers. It then (remembers) the answer for as long as the 's , its time to live, allows. Learn the records you will actually set.

An A record points a name at an IPv4 address and AAAA at an IPv6 address. A CNAME points one name at another name. MX handles email, and TXT is often used to prove you own the domain.

Common trapforgetting caching: after you change a record, clients keep the old answer until its TTL runs out, so lower the TTL a day before a planned move.

A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock

Resources for this stage

Start with· follow one of these

  • GuideFree
    Dev.java: Learn Java

    Oracle · Beginner

    The official path through modern Java: records, collections, generics and exceptions

  • CourseFree
    Java Programming MOOC

    University of Helsinki · Beginner

    Free Helsinki course with hundreds of graded exercises, the best way to get fluent

Practise

  • Exercism

    Your language track: small exercises with free mentor feedback on idiomatic code

Keep handy

  • W3Schools

    Quick syntax lookups for your language when you forget how something is written

  • MDN Web Docs

    Read the HTTP overview, methods, headers and status code pages until they feel obvious

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