Intermediate

A common mistake is shipping your entire build environment — compilers, package managers, SDKs — in your production Docker image. A Go application needs the Go compiler to build. But once it is built, the binary runs without Go installed at all. Why include 1 GB of Go tooling in an image that only needs a 10 MB binary? Multi-stage builds solve this. They let you compile your app in one container and copy only the final artifact into a minimal production image. ...

Containers are ephemeral. When a container stops, all data written inside it disappears. That is fine for stateless apps, but databases and file storage need to persist data. Docker solves this with volumes. And Docker solves container communication with networks. In this tutorial, you will learn both. The Ephemeral Container Problem When you run a PostgreSQL container and insert some rows, that data lives in the container’s writable layer. Stop the container, remove it, and start a new one — the data is gone. ...

Most real applications are not just one container. A typical web app has: A web server (nginx) An API server (your app) A database (PostgreSQL) A cache (Redis) Running four separate docker run commands, connecting them manually, and managing their configuration is painful. Docker Compose solves this. What is Docker Compose? Docker Compose lets you define your entire application stack in a single YAML file. Then you start everything with one command: ...

A Dockerfile is a text file with instructions that tell Docker how to build your image. Every Docker image — from nginx to postgres to your own app — starts with a Dockerfile. In this tutorial, you will learn every key Dockerfile instruction and write a complete, production-ready Dockerfile. Dockerfile Basics A Dockerfile is a plain text file named Dockerfile (no extension). Docker reads it top to bottom when building an image. Each instruction creates a new layer. ...

You have been practicing with SQLite. It is great for learning. But for real projects, you need a real database. PostgreSQL (often called “Postgres”) is the most popular open-source relational database. It is used by companies of all sizes, from startups to enterprises. In this article, you will set it up, connect to it, and learn its unique features. In the previous article, you learned about indexes and performance. Now you will put everything together with a production-ready database. ...

Your queries work. But they are slow. A simple SELECT takes seconds instead of milliseconds. On a table with millions of rows, it could take minutes. The fix is almost always the same: add an index. In the previous article, you learned about window functions. Now you will learn how to make all your queries run fast. What Is an Index? Think of a book’s index at the back. If you want to find “window functions” in a 500-page book, you have two options: ...

GROUP BY is great for summaries. But it collapses your rows. You get one row per group. What if you want the summary and the individual rows at the same time? That is what window functions do. They calculate across rows without removing any of them. In the previous article, you learned about aggregation and subqueries. Window functions are the next level. What Are Window Functions? A window function performs a calculation across a set of rows that are related to the current row. This set of rows is called a window. ...

You know how to get individual rows. But what if you need answers like “How many books did we sell?” or “What is the average book price?” That is where aggregation comes in. In the previous article, you learned how to combine tables with JOINs. Now you will learn how to summarize data across many rows into a single answer. Aggregate Functions Aggregate functions take many rows and return a single value. ...

In the previous tutorials, we learned how to build images, run containers, use Compose, and manage volumes and networks. Everything so far happened on your local computer. Now it is time to deploy. In this tutorial, you will learn how to move your application from your laptop to a production server. The Deployment Workflow Deploying with Docker follows a simple pattern: Build the image on your computer (or in CI/CD) Push the image to a registry Pull the image on the server Run the container on the server Your Computer Registry Server ┌──────────┐ ┌──────────────┐ ┌──────────┐ │ Build │────►│ Docker Hub │────►│ Pull │ │ Image │push │ or ghcr.io │pull │ & Run │ └──────────┘ └──────────────┘ └──────────┘ Docker Hub — The Default Registry Docker Hub is the default place to store and share images. It is free for public images and offers one private repository on the free plan. ...

In the previous tutorial, we used Docker Compose to run an app with a database. We briefly mentioned volumes and networking. Now let’s understand them properly. These two topics answer two important questions: Volumes: How do I keep data when a container is removed? Networking: How do containers talk to each other? Why Containers Lose Data Containers are designed to be temporary. You can create them, destroy them, and replace them. This is a feature, not a bug — it makes containers predictable and easy to deploy. ...