Why caching improves performance in Azure - Why It Works

Introduction

Caching stores copies of data in a fast storage area so that future requests for that data can be served quickly. This reduces the time it takes to get data and lowers the load on the main data source.

When your web app needs to show the same data to many users quickly without asking the database every time

When you want to reduce the cost and delay of repeatedly fetching data from a slow or expensive service

When you want to improve user experience by making pages or features load faster

When you want to handle more users at once without slowing down your system

When you want to avoid repeated calculations by storing results temporarily

Config File - azure-cache-config.json

azure-cache-config.json

{
  "name": "myCache",
  "location": "eastus",
  "sku": {
    "name": "Standard",
    "family": "C",
    "capacity": 1
  },
  "enableNonSslPort": false,
  "redisConfiguration": {
    "maxmemory-policy": "allkeys-lru"
  }
}

This JSON configures an Azure Cache for Redis instance named myCache in the East US region.

The sku section sets the cache size and type.

enableNonSslPort is false to enforce secure connections.

The redisConfiguration sets the eviction policy to remove least recently used keys when memory is full.

Commands

This command creates an Azure Redis Cache instance named 'myCache' in the 'eastus' region under the resource group 'myResourceGroup'. It uses the Standard SKU with a small VM size and disables the non-SSL port for security.

Terminal

az redis create --name myCache --resource-group myResourceGroup --location eastus --sku Standard --vm-size C1 --enable-non-ssl-port false

Expected Output

{

  "id": "/subscriptions/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/resourceGroups/myResourceGroup/providers/Microsoft.Cache/Redis/myCache",

  "location": "eastus",

  "name": "myCache",

  "properties": {

    "provisioningState": "Succeeded",

    "hostName": "myCache.redis.cache.windows.net",

    "port": 6379,

    "sslPort": 6380

  },

  "sku": {

    "name": "Standard",

    "family": "C",

    "capacity": 1

  },

  "type": "Microsoft.Cache/Redis"

}

→

--sku - Sets the cache type and size

→

--enable-non-ssl-port - Disables insecure connections

This command retrieves details about the Redis Cache instance to verify it was created successfully and check its settings.

Terminal

az redis show --name myCache --resource-group myResourceGroup

Expected Output

{

  "id": "/subscriptions/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/resourceGroups/myResourceGroup/providers/Microsoft.Cache/Redis/myCache",

  "location": "eastus",

  "name": "myCache",

  "properties": {

    "provisioningState": "Succeeded",

    "hostName": "myCache.redis.cache.windows.net",

    "port": 6379,

    "sslPort": 6380

  },

  "sku": {

    "name": "Standard",

    "family": "C",

    "capacity": 1

  },

  "type": "Microsoft.Cache/Redis"

}

This command sets a maintenance window on Monday at 2 AM for 60 minutes to apply updates without unexpected downtime.

Terminal

az redis patch-schedule create --name myCache --resource-group myResourceGroup --day-of-week Monday --start-hour 2 --maintenance-window 60

Expected Output

{

  "id": "/subscriptions/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/resourceGroups/myResourceGroup/providers/Microsoft.Cache/Redis/myCache/patchSchedules/Default",

  "dayOfWeek": "Monday",

  "startHourUtc": 2,

  "maintenanceWindow": 60

}

→

--day-of-week - Specifies the day for maintenance

→

--start-hour - Specifies the hour to start maintenance

Key Concept

If you remember nothing else from this pattern, remember: caching stores data closer to where it is needed to make access much faster and reduce load on slower sources.

Common Mistakes

Not disabling the non-SSL port when creating the cache

This allows insecure connections that can expose data to attackers

Always set --enable-non-ssl-port false to enforce secure connections

Not verifying the cache creation with az redis show

You might think the cache is ready when it is still provisioning or failed

Run az redis show to confirm the cache is provisioned and ready

Not setting a maintenance window

Updates can happen at unexpected times causing downtime

Use az redis patch-schedule create to set a predictable maintenance time

Summary

Create an Azure Redis Cache instance with secure settings using az redis create.

Verify the cache is ready with az redis show before using it.

Set a maintenance window to control when updates happen and avoid surprises.

Practice

1. Why does caching improve performance in cloud applications?

easy

A. It slows down data retrieval to save energy

B. It increases the size of the database

C. It deletes old data to free up space

D. It stores frequently used data to avoid repeated slow access

Solution

1. Step 1: Understand caching purpose

   Caching keeps copies of data that are used often, so the system doesn't have to fetch them repeatedly from slow storage.

2. Step 2: Identify performance impact

   By avoiding repeated slow access, caching speeds up data retrieval and reduces wait times for users.

3. Final Answer:

   It stores frequently used data to avoid repeated slow access -> Option D

4. Quick Check:

   Caching = storing frequent data for speed [OK]

Hint: Caching stores frequent data to speed up access [OK]

Common Mistakes:

• Thinking caching increases database size
• Confusing caching with data deletion
• Believing caching slows down retrieval

2. Which Azure service is commonly used to implement caching for web applications?

easy

A. Azure Blob Storage

B. Azure SQL Database

C. Azure Cache for Redis

D. Azure Virtual Machines

Solution

1. Step 1: Identify caching service in Azure

   Azure Cache for Redis is a managed caching service designed to store and retrieve data quickly.

2. Step 2: Compare with other services

   Blob Storage stores files, SQL Database stores structured data, and Virtual Machines run applications but do not provide caching directly.

3. Final Answer:

   Azure Cache for Redis -> Option C

4. Quick Check:

   Azure caching = Azure Cache for Redis [OK]

Hint: Redis is the caching service in Azure [OK]

Common Mistakes:

• Choosing Blob Storage as cache
• Confusing SQL Database with cache
• Selecting Virtual Machines for caching

3. Consider this Azure caching scenario:

cache = AzureCache()
cache.set('user_1', 'Alice')
value = cache.get('user_1')

What will be the value of value after these operations?

medium

A. 'Alice'

B. 'user_1'

C. Error: Key not found

D. None

Solution

1. Step 1: Understand cache set operation

   The set method stores the value 'Alice' with the key 'user_1' in the cache.

2. Step 2: Understand cache get operation

   The get method retrieves the value stored with key 'user_1', which is 'Alice'.

3. Final Answer:

   'Alice' -> Option A

4. Quick Check:

   Cache get after set returns stored value [OK]

Hint: Get returns the value set for the key [OK]

Common Mistakes:

• Expecting None if key exists
• Confusing key and value
• Assuming error if key is present

4. A developer notices that cached data is not updating after changes in the database. What is the likely cause?

medium

A. Database is offline

B. Cache expiration time is too long

C. Cache is automatically syncing with database

D. Cache size is too small

Solution

1. Step 1: Identify caching update issue

   If cached data stays the same after database changes, it means the cache is serving old data.

2. Step 2: Understand cache expiration role

   Long expiration time means cached data stays valid longer, delaying updates from the database.

3. Final Answer:

   Cache expiration time is too long -> Option B

4. Quick Check:

   Long cache expiry delays data refresh [OK]

Hint: Long cache expiry causes stale data [OK]

Common Mistakes:

• Assuming database offline causes stale cache
• Thinking cache auto-syncs always
• Believing cache size affects data freshness

5. You want to improve performance of an Azure web app that reads product details frequently but updates rarely. Which caching strategy is best?

hard

A. Cache product details with a long expiration time and refresh manually on updates

B. Disable caching to always get fresh data

C. Cache product details with very short expiration time (few seconds)

D. Cache only user session data, not product details

Solution

1. Step 1: Analyze data usage pattern

   Product details are read often but updated rarely, so caching them reduces repeated database reads.

2. Step 2: Choose caching strategy

   Long expiration avoids frequent cache refreshes, and manual refresh on updates keeps data accurate.

3. Final Answer:

   Cache product details with a long expiration time and refresh manually on updates -> Option A

4. Quick Check:

   Long cache + manual refresh suits rare updates [OK]

Hint: Long cache with manual refresh fits rare updates [OK]

Common Mistakes:

• Disabling cache wastes performance gains
• Using short expiration causes frequent reloads
• Ignoring caching product details