DEV Community: elysianx

How to Start Docker for Beginners

elysianx — Fri, 03 Jul 2026 14:00:38 +0000

What's Docker

Docker is a containerization platform that packages applications with all dependencies into portable utils called containers.

Learn the foundational concepts of `Docker`

Core concepts:

Image: A read-only blueprint containing app code,libraries,and environment settings.
Container: A running instance of an image.
Dockerfile: Script defining how to build an image.
Volume: Persistent storage outside the container lifecycle.
Network: Enables communication between containers.

Example: Building and Running a Container

FROM node:18
WORKDIR /app
COPY package.json ./
RUN npm install
COPY .
EXPOSE 3000
CMD ["npm", "start"]

docker build -t my-node-app

docker run -p 3000:3000 my-node-app

Managing Multi-Container Apps with Docker Compose

version: '3'
services:
 app:
   build:
   ports:
     - "3000:3000"
   depends_on:
     - mongo
 mongo:
   image: mongo
   volumes:
     - mongo-data:/data/db
volumes:
 mongo-data:

RUN with:

docker-compose up

Best Practices

Use .dockerignore to exclude unnecessary files(e.g.,.git,node_modules).
Avoid :latest tags;pin versions for stability.
Run containers as non-root for security.
Use multi-stage builds to reduce image size.
Store secrets in .env files or Docker secrets, not in images.

When to Use Docker

[Y] Consistent dev/prod environments
[N] Small static sites or quick scripts where setup overhead outweighs benefits.

Next Steps

Learn Docker networking(bridge, host, overlay)for container communication.
Explore Docker volumes for persistent data.
Integrate Docker into CI/CD pipelines for automated builds and deployments.

With these fundamentals, you can confidently containerize, run, and manage applications in any environment.

How to Submit the First Formal PR for Beginners?

elysianx — Thu, 02 Jul 2026 13:39:35 +0000

After spending some time contributing to open source,I’ve realized the biggest hurdle for beginners isn’t finding a sustainable project-it’s submitting your first PR. If you’re also a beginner aiming to create your first PR, keep reading.

Step 1:Prepare

If you don't have git on your machine, install it.

Step 2:Fork this repository

Fork this repository by clicking on the fork button on the top of this page.
This will create a copy of this repository in your account.

Step 3:Clone the repository

Now clone the forked repository to your machine. Go to your GitHub account, open the forked repository, click on the code button, then on SSH tab and then click the copy url to clipboard icon.

Open a terminal and run the following git command:

git clone "url you just copied"

Step 4:Find a `good-first-issue`

Now search for an issue you like

Communicate with the maintainer about what you should do! Don't worry you can't do it well. You will be assigned, then work.

Step 5:Create a branch

Change to the repository directory on your computer

cd my-first-contributions

Make necessary changes and commit those changes

Open Contributors.md file in a text editor and issue,add your name to it.Save your file.

If you go to the project directory and execute the command git status, you'll see there are changes.

Add those changes to the branch you just created using the git add command:

git add Contributors.md

Now commit those changes using the git commit command:

git commit -m "Add your-name to Contributors list"

replacing your-name with your name.

Push changes to GitHub

Push your changes using the command git push:

git push -u origin your-branch-name

replacing your-branch-name with the name of the branch you created earlier.

Communicate with the maintainer about what to do. Don't worry if it's not perfect — they'll guide you. Get assigned, then get to work.

I Build a blog API with Redis - Here's every problem I Hit

elysianx — Tue, 23 Jun 2026 14:21:13 +0000

I build a blog API with FastAPI + Redis + MySQL.
Three cache problems almost killed my app.
If you also face these problems!
Here's how I fixed each one.

1. Cache Penetration

What's Cache Penetration?

Cache Penetration refers to a scenario where the requested data exists neither in cache nor in the database,causing every request to hit the database directly,thereby increasing the database load.

How to solve?

1.Caching null values

Steps:

When a queried key exists in neither the cache nor the database,the result (such as null or an empty value) is cached with a short TTL.
This way,subsequent identical requests can be served directly from the cache,avoiding frequent database access.

Example:

...
redis = get_redis()
data = redis.get(cache_key)

# First, check the cache. If the cache entry exists, check whether it is __NULL__
if data is not None:
    if data == "__NULL__":
        return {"data": None, "source": "cache"}
    return {"data": data, "source": "cache"}

# Second, cache miss, query database
value = query_database(cache_key)

# Third, cache the result whether it exists in DB or not
if value is not None:
    redis.setex(cache_key, 60, value)          # cache real data
else:
    redis.setex(cache_key, 10, "__NULL__")     # cache null sentinel (short TTL)

return value

2.Cache breakdown

What's Cache breakdown?

Cache breakdownoccurs when a popular data entry expires in the cache while a massive number of concurrent requests are hitting that same data at the exact same time.All those requests penetrate straight through to the database,putting enormous pressure on it and potentially causing system performance issues.

How to solve?

Lock mechanism:When the cache expires,use a locking mechanism to ensure that only one thread can access the database and update the cache.The other threads wait util the cache is rebuilt before reading the data.

Example:

# Generate a lock key based on the given key
lock_key = f"mutex:{key}"

# Use SETNX operation to acquire the lock. If the key does not exist, set it with an expiration time of 300 seconds.
# This prevents concurrent access.
lock_acquired = redis_client.set(lock_key, "1", nx=True, ex=300)

if lock_acquired:
    try:
        # Successfully acquired the lock, query the database
        value = db_query_func(key)
        if value is not None:
            # Write the result to the cache with an expiration time of 3600 seconds
            redis_client.setex(key, 3600, value)
        return value
    finally:
        # Release the lock
        redis_client.delete(lock_key)
else:
    # Failed to acquire the lock, sleep for 0.1 seconds and then retry
    time.sleep(0.1)
    return get_data_with_mutex(key, redis_client, db_query_func)

3.Cache avalanche

What's cache avalanche?

Cache avalancerefers to a situation where a large amount of cached data expires at the same time or the cache service goes down. As a result, all requests are directly sent to the database, causing a sudden surge in the database's pressure and even leading to its downtime.

How to solve?

Randomized TTL

The core idea is to avoid a large number of keys expiring simultaneously.
When setting the expiration time for the cache, add a random value.

Example:

import random

expire_time = time + random.randint(0,300)
redis.set(key,value,ex=expire_time)

What about you?

Have you run into any of these cache problems in your projects?
Or do you use a different strategy? Let me know in the comments 👇

If this was helpful, follow me for more backend deep dives.

DEV Community: elysianx

How to Start Docker for Beginners

What's Docker

Learn the foundational concepts of Docker

Core concepts:

Example: Building and Running a Container

Managing Multi-Container Apps with Docker Compose

Best Practices

When to Use Docker

Next Steps

How to Submit the First Formal PR for Beginners?

Step 1:Prepare

If you don't have git on your machine, install it.

Step 2:Fork this repository

Step 3:Clone the repository

Step 4:Find a good-first-issue

Step 5:Create a branch

Make necessary changes and commit those changes

Push changes to GitHub

I Build a blog API with Redis - Here's every problem I Hit

1. Cache Penetration

What's Cache Penetration?

How to solve?

1.Caching null values

2.Cache breakdown

What's Cache breakdown?

How to solve?

3.Cache avalanche

What's cache avalanche?

How to solve?

What about you?

Learn the foundational concepts of `Docker`

Step 4:Find a `good-first-issue`