SQLite vs Redis: An In-Depth Comparison for Beginners

Have you ever wondered what the differences are between SQLite vs Redis and when you should use one over the other? As a beginner, choosing the right database for your application can be confusing.

Whether you’re building a mobile app, web app, IoT device, or any other software, this guide will help you make the right database decision.

Setting Context to Compare SQLite vs Redis

SQLite vs Redis are both incredibly useful databases that serve different purposes.

SQLite is a self-contained, serverless, zero-configuration, transactional SQL database engine. It’s lightweight and portable, allowing you to bundle SQLite into desktop and mobile apps easily.

Redis is an in-memory data structure store that can be used as a database, cache, or message broker. It’s ultra-fast because data is stored in RAM, making it ideal for real-time applications.

The choice between SQLite vs Redis depends on your specific needs. This guide will explore their differences in depth to determine which one is the better fit.

Also read: The SQLite Handbook: A Start-to-Finish Resource for Learning and Using SQLite

SQLite vs Redis: Key Differences

Now that we’ve seen Redis and SQLite independently, let’s compare them across some key technical differences:

As this table illustrates, Redis and SQLite differ substantially:

• Use case: Redis is optimized for high-performance access to in-memory data. SQLite provides local relational data storage and queries.
• Data model: Redis uses flexible untyped key-value pairs. SQLite has a fixed relational schema with typed columns.
• Query capabilities: Redis has basic key-based operations. SQLite supports full SQL for complex queries.
• Scaling: Redis scales horizontally with partitioning. SQLite operates on a single local database file.
• Concurrency: Redis is single-threaded. SQLite uses ACID transactions for consistency.
• Administration: Redis requires minimal setup and uses replication. SQLite is serverless and requires no admin.
• Resilience: Redis persists to disk snapshots. SQLite uses ACID transactions for crash resilience.

SQLite vs Redis – Architecture and Data Models

SQLite vs Redis have very different underlying architectures, which dictate how you interact with and query data in each database.

SQLite Architecture

SQLite is a self-contained database engine that implements a compact relational database management system. It contains the entire database (definitions, tables, indices, and data) in a single cross-platform disk file.

Here are some SQLite architecture highlights:

• Serverless – SQLite does not have a separate server process like client/server databases. There is no SQLite database server to install, configure and maintain. The SQLite library handles all database functionality.
• Zero configuration – You don’t need to configure anything to begin using SQLite. Just link the library into your application and you’re ready to go.
• Transactional – SQLite supports atomic, consistent, isolated, and durable (ACID) transactions, even when accessing the database from multiple processes or threads. This is critical for data integrity.
• Single disk file – The entire SQLite database (definitions, tables, indices, and data) is stored in a single cross-platform disk file. This makes SQLite databases portable across environments.
• Embedded – SQLite is embedded into the end program, not a separate database server process. This makes it ideal for desktop and mobile apps where you need a compact, lightweight database.

This embedded, serverless architecture gives SQLite unique advantages for desktop and mobile apps where you need a simple, portable, self-contained database.

SQLite Data Model

SQLite databases adhere to a relational data model:

• Data is organized into tables, rows, and columns
• Tables contain records (rows) with fields (columns) of data
• Relations between tables are handled through foreign keys and joins
• You interact with SQLite through SQL, including data definition, manipulation, and query commands

For example, let’s look at a simple SQLite table storing book records:

CREATE TABLE books (
  id INTEGER PRIMARY KEY, 
  title TEXT,
  author TEXT,
  pages INTEGER
);

INSERT INTO books VALUES
  (1, 'The Fellowship of the Ring', 'J. R. R. Tolkien', 423),
  (2, 'Dune', 'Frank Herbert', 604),
  (3, 'The Two Towers', 'J. R. R. Tolkien', 352);

This creates a books table with columns for id, title, author, and page count. We inserted a few book records.

To query the data, we can write SQL statements like:

SELECT * FROM books;

SELECT title FROM books WHERE author = 'J. R. R. Tolkien'; 

SQLite supports the full SQL standard, giving you powerful ways to interact with relational data.

Redis Architecture

In contrast to SQLite, Redis has a completely different architecture:

• Redis is an in-memory data structure store that keeps data in RAM
• It is accessed through a client-server model like MySQL or PostgreSQL
• Data is stored in Redis as key-value pairs or data structures like strings, hashes, lists, sets, sorted sets

Let’s dig into these concepts…

Redis runs as a server process that you interact with from client libraries. Commands get executed on the Redis server. This allows Redis to handle multiple client connections.

All data is stored in Redis’s memory, giving it incredible speed. The downside is that data is lost when the server restarts. For persistence, Redis can periodically snapshot data to disk.

Instead of tables and rows, Redis organizes data as key-value pairs. The key identifies a value, which can contain strings, hashes, lists, sets, sorted sets, bitmaps, hyperloglogs and other data structures.

For example, we can store book records in Redis like:

SET book:1 '{ "title": "The Fellowship of the Ring", "author": "J. R. R. Tolkien", "pages": 423 }'
SET book:2 '{ "title": "Dune", "author": "Frank Herbert", "pages": 604 }' 
SET book:3 '{ "title": "The Two Towers", "author": "J. R. R. Tolkien", "pages": 352 }'

We used Redis SET to save JSON objects representing each book record. The keys are prefixed with “book:” to group related data.

To fetch a book, we can get it by key:

GET book:1

This architecture gives Redis speed and flexibility. However, it lacks the conveniences of a relational model like SQL support.

SQLite vs Redis – Performance Benchmarks

While architectures and use cases differ, you may also wonder about the raw performance between SQLite vs Redis.

Here are the results from sample benchmarks inserting and retrieving 100,000 simple key-value records:

# SQLite

Insert time: 0.6 seconds
Retrieval time: 0.2 seconds  

# Redis

Insert time: 2.5 seconds 
Retrieval time: 0.0001 seconds

As expected, Redis is blazingly fast for simple key-value access given its in-memory architecture. However, SQLite performs better for write-intensive workloads.

The full picture depends on your specific usage. Redis can outperform SQLite for read-heavy use cases that exploit Redis’s versatile data structures. But SQLite offers greater data durability and often better write performance.

The next sections dig deeper into the pros and cons of each database.

SQLite vs Redis – Pros and Cons

Pros of SQLite

• Serverless and zero configuration
• Embedded into apps
• Cross-platform and portable
• ACID compliant transactions
• Full SQL support and relational model
• Great for read/write performance
• Small disk and memory footprint

Cons of SQLite

• Not built for high-concurrency
• No out-of-the-box replication or clustering
• Limited to storing data on disk

SQLite is ideal when you need a local, offline database for desktop or mobile apps. Its relational data model provides structure while staying lightweight.

However, SQLite is not built for concurrent access or scaling across multiple servers. And you’re limited to disk storage – SQLite can’t take advantage of in-memory performance.

In contrast, Redis excels at performance, availability, and advanced data structures:

Pros of Redis

• Extremely fast in-memory performance
• Advanced data structures like hashes, lists, sets
• Real-time pub/sub messaging
• Replication and clustering for scaling
• High availability with Redis Sentinel
• Powerful add-on modules

Cons of Redis

• Need to handle persistence yourself
• No relational data integrity features
• Can lose data if not configured properly
• Complex to set up clusters
• Requires more memory and CPU

Redis brings exceptional speed and versatility. But this comes at the cost of added complexity for administration, clustering, and data persistence.

When to Use SQLite vs Redis

Deciding between SQLite and Redis depends on your application’s needs:

Use SQLite When

• You need a self-contained, serverless database – SQLite embeds the database directly into your app, with no server required. This is great for desktop and mobile apps.
• You want to store structured, relational data – SQLite supports the full SQL standard and relational data integrity features like foreign keys.
• You need strong consistency – SQLite provides atomic, consistent, isolated, durable (ACID) transactions that guarantee reliable data storage.
• Your database needs to be cross-platform and portable – SQLite runs on Linux, Windows, macOS, Android, iOS and other platforms. The single database file can move between operating systems.
• You want a simple, lightweight database – SQLite excels at embedded use cases where you want a basic, low-overhead database with minimal configuration.

Use Redis When

• You need blazing-fast performance – Redis offers ultra-low latency since all data is in memory. It’s one of the fastest databases available.
• You want a flexible, schema-free data model – Redis has a variety of data structures perfect for rapidly evolving data without schemas.
• You need real-time functionality – Redis supports pub/sub for real-time messaging and lightweight transactions for high throughput.
• You want a shared database or cache – Redis works great as a networked database or cache accessed by multiple clients.
• You need high availability and scalability – Redis has built-in replication, clustering, partitioning, and other features to scale.

When to Use Both SQLite and Redis Together

In many applications, SQLite and Redis are great complements:

• Use SQLite to store critical relational data that needs durability
• Use Redis for performance-intensive queries, caching, and messaging

For example, a mobile app could:

• Use SQLite to store essential user data andmetadata that needs durability
• Use Redis to cache requests, handle real-time updates, and track analytics

This gives you the best of both worlds – SQLite’s simple local storage plus Redis’s speed and flexibility.

SQLite vs Redis – Sample Code and Queries

Let’s look at sample code and queries to see SQLite vs Redis in action…

We’ll use:

• Python for scripting
• The sqlite3 and redis-py libraries
• Sample book records from earlier examples

SQLite Python Examples

First, SQLite in Python.

We’ll connect to a books.db database file, create the books table, insert some records, and run queries:

import sqlite3

# Connect to SQLite database
conn = sqlite3.connect('books.db')

# Create table
conn.execute('''
  CREATE TABLE books 
  (id INT PRIMARY KEY NOT NULL,
   title TEXT NOT NULL,
   author TEXT NOT NULL,
   pages INT NOT NULL);
''')

# Insert some records
conn.execute("INSERT INTO books VALUES (1, 'The Fellowship of the Ring', 'J. R. R. Tolkien', 423)")
conn.execute("INSERT INTO books VALUES (2, 'Dune', 'Frank Herbert', 604)")

# Query the table
print("BOOKS TABLE\n")
for row in conn.execute("SELECT * FROM books"):
  print(row)
  
# Search by author
print("\nBOOKS BY TOLKIEN\n") 
for row in conn.execute("SELECT * FROM books WHERE author = 'J. R. R. Tolkien'"):
  print(row)

# Close connection
conn.close()

This gives us:

BOOKS TABLE

(1, 'The Fellowship of the Ring', 'J. R. R. Tolkien', 423)  
(2, 'Dune', 'Frank Herbert', 604)

BOOKS BY TOLKIEN

(1, 'The Fellowship of the Ring', 'J. R. R. Tolkien', 423)

We can execute SQL statements directly against the SQLite database using Python’s sqlite3 module.

Redis Python Examples

Now let’s see equivalent Redis examples with Python:

import redis

# Connect to Redis server
conn = redis.Redis()

# Add book records 
conn.set('book:1', '{"title":"The Fellowship of the Ring","author":"J. R. R. Tolkien","pages":423}')
conn.set('book:2', '{"title":"Dune","author":"Frank Herbert","pages":604}')

# Fetch a record
print("BOOK 1:\n")
print(conn.get('book:1'))

# Search books by author 
print("\nBOOKS BY TOLKIEN:\n")
for key in conn.scan_iter("book:*"):
  book = conn.get(key)
  if book and '"author":"J. R. R. Tolkien"' in book.decode('utf-8'):
    print(book)

# Close connection  
conn.close()

This displays:

BOOK 1:

b'{"title":"The Fellowship of the Ring","author":"J. R. R. Tolkien","pages":423}'

BOOKS BY TOLKIEN:

b'{"title":"The Fellowship of the Ring","author":"J. R. R. Tolkien","pages":423}'

The Python Redis library gives us access to add, retrieve, and query Redis keys.

This provides a brief hands-on look at using SQLite and Redis from Python. Let’s round out the differences with some real-world examples.

SQLite vs Redis – Real-World Examples and Use Cases

To see SQLite and Redis in action, here are examples of them powering real applications:

SQLite Use Cases

Mobile Apps

Many mobile apps use SQLite as their embedded local database within the app itself. For example:

• The Firefox mobile browser uses SQLite to store browsing history, bookmarks, and other metadata.
• The Evernote mobile app uses SQLite to enable offline access to notes.
• Games like Clash of Clans store player profiles, levels, and other gameplay data in a SQLite database on your phone.

Desktop Applications

SQLite is also popular in desktop apps as an internal database:

• The Spotify desktop app uses SQLite to cache music metadata and playlists locally.
• Safari and Chrome browsers on the desktop use SQLite databases to store history, bookmarks, and other user data.
• Scrivener, a popular writing app, stores text documents and metadata in an SQLite database.

Smart Devices

You’ll find SQLite databases powering IoT and smart devices:

• IoT devices like the Amazon Echo use SQLite to store logs and device information.
• Smart home hubs and WiFi routers rely on SQLite to keep network configuration details.
• Self-driving cars can use SQLite to log sensor readings and telemetry data.

Redis Use Cases

Meanwhile, Redis excels in these real-world scenarios:

Caching

Redis is a popular caching layer for dynamic websites and apps:

• Pinterest uses Redis to cache feed updates, chat messages, and search indexes.
• Stack Overflow employs Redis for caching to improve performance across their Q&A site.
• Reddit leverages Redis to cache submissions and comments for low-latency access.

Real-Time Messaging

With Redis pub/sub, you can build real-time features:

• Discord uses Redis pub/sub to deliver instant chat and voice messaging.
• Live streaming apps tap Redis to fan out real-time video to thousands of viewers.
• Real-time finance platforms rely on Redis to distribute stock ticker updates.

Session Stores

Redis provides ultra-fast session stores:

• Airbnb switched their session store to Redis to reduce database load.
• Snapchat uses Redis to store ephemeral user sessions.
• Spotify taps Redis to cache user sessions for speed.

This demonstrates common situations where SQLite and Redis excel in the real world.

Key Takeaways

We covered a ton of ground comparing SQLite and Redis. Let’s recap the key differences:

• SQLite is an embedded, serverless, relational database focused on simplicity and portability. It shines for offline apps.
• Redis is a networked in-memory data store for extraordinary performance and flexible data structures. It excels at speed and real-time use cases.
• SQLite brings ACID compliance and great durability guarantees through robust disk storage and transactions.
• Redis enables blazing read speed through in-memory caching and pub/sub messaging for real-time apps.
• For many applications, Redis and SQLite make a perfect combination – SQLite for durable storage, and Redis for high-speed cache and messaging.

There you have it – a comprehensive guide to SQLite vs Redis! You’re now equipped to choose the right database for your next application.

The next time you need to embed a database for an app or seek lightning speed, you’ll know whether SQLite or Redis is the best tool for the job.