Why configuration matters in Redis - See It in Action

Why Configuration Matters in Redis

📖 Scenario: You are setting up a Redis database for a small online store. Redis will store product stock counts so the store can quickly check availability.

🎯 Goal: Build a simple Redis setup where you create initial stock data, configure a threshold for low stock, check stock levels, and mark products as low stock if needed.

📋 What You'll Learn

Create a Redis hash called product_stock with exact product stock counts

Add a configuration variable low_stock_threshold with value 5

Write a Redis Lua script that checks each product's stock against low_stock_threshold

Add a Redis set low_stock_products to store products below the threshold

💡 Why This Matters

🌍 Real World

Retailers use Redis to quickly check product availability and alert when stock is low to reorder.

💼 Career

Understanding Redis data structures and Lua scripting is valuable for backend developers working on fast, scalable inventory systems.

1

DATA SETUP: Create initial product stock data

Create a Redis hash called product_stock with these exact entries: "apple": "10", "banana": "3", "orange": "7".

Redis

# Create the Redis hash product_stock with given products and stock counts
# Your code here

Need a hint?

Use the HSET command to create a hash with multiple fields and values.

2

CONFIGURATION: Set low stock threshold

Create a Redis string key called low_stock_threshold and set its value to 5.

Redis

HSET product_stock apple 10 banana 3 orange 7
# Set low_stock_threshold to 5
# Your code here

Need a hint?

Use the SET command to store a simple configuration value.

3

CORE LOGIC: Check stock levels with Lua script

Write a Redis Lua script that iterates over all products in product_stock, compares each stock count to the low_stock_threshold, and returns a list of products below the threshold. Use redis.call and for loop with variables i and product.

Redis

HSET product_stock apple 10 banana 3 orange 7
SET low_stock_threshold 5
-- Write Lua script to find products below low_stock_threshold
-- Your code here

Need a hint?

Use HKEYS to get all product names, GET to get the threshold, and loop through products to compare stock.

4

COMPLETION: Store low stock products in a Redis set

Use the Lua script to add each product below the threshold into a Redis set called low_stock_products using redis.call('SADD', 'low_stock_products', product) inside the loop.

Redis

HSET product_stock apple 10 banana 3 orange 7
SET low_stock_threshold 5
local products = redis.call('HKEYS', 'product_stock')
local threshold = tonumber(redis.call('GET', 'low_stock_threshold'))
local low_stock = {}
for i, product in ipairs(products) do
  local stock = tonumber(redis.call('HGET', 'product_stock', product))
  if stock < threshold then
    table.insert(low_stock, product)
    -- Add product to low_stock_products set
    -- Your code here
  end
end
return low_stock

Need a hint?

Use SADD inside the loop to add products to the set.