The Database Systems Landscape

Build the mental model

Stepping back from any single technology, it helps to see where each major database sits on the map.

PostgreSQL and MySQL are both general-purpose relational databases. This site has a PostgreSQL course but not yet a MySQL one - conceptually they play a similar role. Neither is a universal winner.

SQLite is an embedded, file-based relational database - not a network server. The next lesson goes deeper.

MongoDB represents the document-database approach and Redis represents the key-value/caching approach - both covered in their own dedicated courses on this site.

Supabase Database is a managed platform built on PostgreSQL; its hands-on depth lives in the Cloud Providers & Platforms course's Supabase lesson.

DATABASE SYSTEMS LANDSCAPE
--------------------------
RELATIONAL             DOCUMENT        KEY-VALUE
PostgreSQL, MySQL      MongoDB         Redis
(server, general use)  (flexible docs) (cache, fast lookups)

SQLite
(embedded, single-file, no server process)

MANAGED PLATFORM
Supabase Database (managed PostgreSQL + auth, storage, APIs)

Connect it to a real scenario

Need a general-purpose relational database? PostgreSQL (or MySQL) is a safe default. Need one that ships inside your app with no server? SQLite fits that role.

Need to store content that doesn't fit rigid tables? Look at MongoDB. Need blazing-fast lookups for sessions, caches, or leaderboards? Redis is built for that.

If you want to skip infrastructure work with a managed Postgres that bundles authentication and instant APIs, evaluate Supabase Database.

The runnable example below turns this checklist into a small function.

• PostgreSQL and MySQL are both general-purpose relational databases with no universal winner between them
• SQLite plays the embedded/file-based role, MongoDB the document role, and Redis the key-value/cache role in the landscape
• Supabase Database is managed PostgreSQL plus extras, with its own hands-on depth in the Cloud Providers & Platforms course

Try the working example

function suggestSystem(need) {
  const map = {
    "general web app relational data":
      "PostgreSQL (or MySQL) - general-purpose relational database. Continue: the PostgreSQL course.",
    "embedded mobile app storage":
      "SQLite - embedded, file-based database. Continue: this course's SQLite lesson.",
    "flexible document data":
      "MongoDB - document database. Continue: the MongoDB course.",
    "fast cache/session store":
      "Redis - key-value store. Continue: the Redis course.",
    "managed Postgres with built-in auth":
      "Supabase Database - managed PostgreSQL plus extras. Continue: the Supabase lesson in Cloud Providers & Platforms.",
  };
  return map[need] || "Not on this map yet - describe the need more specifically.";
}

[
  "general web app relational data",
  "embedded mobile app storage",
  "flexible document data",
  "fast cache/session store",
  "managed Postgres with built-in auth",
].forEach((need) => console.log(`${need} ->`, suggestSystem(need)));

general web app relational data -> PostgreSQL (or MySQL) - general-purpose relational database. Continue: the PostgreSQL course.
embedded mobile app storage -> SQLite - embedded, file-based database. Continue: this course's SQLite lesson.
flexible document data -> MongoDB - document database. Continue: the MongoDB course.
fast cache/session store -> Redis - key-value store. Continue: the Redis course.
managed Postgres with built-in auth -> Supabase Database - managed PostgreSQL plus extras. Continue: the Supabase lesson in Cloud Providers & Platforms.

All five example needs map cleanly to a system and the course to continue to for depth.

Wikipedia: Comparison of relational database management systems — How Databases Work