Hash tables in caching (Redis, Memcached) in Data Structures Theory - Mini Project: Build & Apply

Hash Tables in Caching (Redis, Memcached)

📖 Scenario: You are learning how caching systems like Redis and Memcached use hash tables to store and retrieve data quickly. Imagine a simple cache that holds user session data for a website. Each session has a unique session ID and some user information.

🎯 Goal: Build a simple representation of a cache using a hash table (dictionary) that stores session IDs as keys and user names as values. Then, set a limit for the cache size, add new sessions, and finally retrieve a session's user name using the session ID.

📋 What You'll Learn

Create a dictionary called cache with three session ID and user name pairs.

Create a variable called max_cache_size and set it to 5.

Add a new session ID and user name pair to the cache dictionary.

Retrieve the user name for a given session ID from the cache dictionary.

💡 Why This Matters

🌍 Real World

Caching systems like Redis and Memcached use hash tables to quickly store and retrieve data such as user sessions, improving website speed and performance.

💼 Career

Understanding hash tables in caching is important for roles in backend development, system design, and performance optimization.

1

Create the initial cache dictionary

Create a dictionary called cache with these exact entries: 'sess1': 'Alice', 'sess2': 'Bob', and 'sess3': 'Charlie'.

Data Structures Theory

# Create the cache dictionary with three session entries
# Your code here

Need a hint?

Use curly braces {} to create a dictionary with keys and values separated by colons.

2

Set the maximum cache size

Create a variable called max_cache_size and set it to 5 to represent the cache size limit.

Data Structures Theory

cache = {'sess1': 'Alice', 'sess2': 'Bob', 'sess3': 'Charlie'}
# Set the max_cache_size variable to 5
# Your code here

Need a hint?

Just assign the number 5 to the variable max_cache_size.

3

Add a new session to the cache

Add a new entry to the cache dictionary with the key 'sess4' and the value 'Diana'.

Data Structures Theory

cache = {'sess1': 'Alice', 'sess2': 'Bob', 'sess3': 'Charlie'}
max_cache_size = 5
# Add 'sess4': 'Diana' to the cache dictionary
# Your code here

Need a hint?

Use square brackets with the key inside to add a new key-value pair to the dictionary.

4

Retrieve a user name from the cache

Retrieve the user name stored in cache for the session ID 'sess2' and assign it to a variable called user_name.

Data Structures Theory

cache = {'sess1': 'Alice', 'sess2': 'Bob', 'sess3': 'Charlie'}
max_cache_size = 5
cache['sess4'] = 'Diana'
# Retrieve the user name for 'sess2' and assign it to user_name
# Your code here

Need a hint?

Use the session ID as the key inside square brackets to get the value from the dictionary.