Cache-aside pattern in Azure - Step-by-Step Execution

Process Flow - Cache-aside pattern

Request data

↓

Check cache

↓

Store in cache

↓

Return data

This flow shows how the cache-aside pattern works: first check cache, if data is missing, get it from database, store it in cache, then return it.

Execution Sample

Azure

def get_data(key):
    data = cache.get(key)
    if data is None:
        data = database.get(key)
        cache.set(key, data)
    return data

This code tries to get data from cache first; if not found, it fetches from database, caches it, then returns.

Process Table

Step	Action	Cache State	Database Access	Returned Data
1	Request data with key 'user123'	{}	No	None
2	Check cache for 'user123'	{}	No	None
3	Cache miss, fetch from database	{}	Yes	UserData123
4	Store 'UserData123' in cache	{'user123': 'UserData123'}	No	UserData123
5	Return data 'UserData123'	{'user123': 'UserData123'}	No	UserData123
6	Next request for 'user123'	{'user123': 'UserData123'}	No	UserData123
7	Check cache for 'user123'	{'user123': 'UserData123'}	No	UserData123
8	Cache hit, return cached data	{'user123': 'UserData123'}	No	UserData123

💡 Execution stops after returning cached data on second request.

Status Tracker

Variable	Start	After Step 3	After Step 4	After Step 8
cache	{}	{}	{'user123': 'UserData123'}	{'user123': 'UserData123'}
data	None	UserData123	UserData123	UserData123

Key Moments - 3 Insights

Why do we check the cache before the database?

Because checking the cache first avoids unnecessary database calls, improving speed and reducing load, as shown in steps 2 and 7 where cache is checked first.

What happens when the data is not in the cache?

When data is missing in cache (step 3), the system fetches it from the database and then stores it in cache (step 4) for future requests.

Why do we store data in cache after fetching from database?

Storing data in cache after fetching ensures next requests get faster responses without hitting the database again, as seen in step 4 and step 8.

Visual Quiz - 3 Questions

Look at the execution table, what is the cache state after step 4?

A {'user123': 'UserData123'}

B None

C {}

D {'user123': None}

💡 Hint

Check the 'Cache State' column in row for step 4.

At which step does the system access the database?

A Step 2

B Step 3

C Step 6

D Step 7

💡 Hint

Look at the 'Database Access' column to find 'Yes'.

If the cache already contains the data, what changes in the execution table?

A Data is fetched twice from database

B Cache is cleared

C Database access is skipped

D Returned data is None

💡 Hint

Refer to steps 6-8 where cache hit avoids database access.

Concept Snapshot

Cache-aside pattern:
- Check cache first for data
- If missing, fetch from database
- Store fetched data in cache
- Return data to requester
Improves performance by reducing database load.

Full Transcript

The cache-aside pattern works by first checking if the requested data is in the cache. If it is, the data is returned immediately, avoiding a database call. If the data is not in the cache, the system fetches it from the database, stores it in the cache for future use, and then returns it. This pattern helps improve application speed and reduces database load by caching frequently accessed data.