Micro-caching for dynamic content in Nginx - Step-by-Step Execution

Process Flow - Micro-caching for dynamic content

Client Request Arrives

↓

Check Cache for Response

↓

Cache Hit

↓

Serve Cached

↓

Store Response in Cache

↓

Send to Client

When a client requests dynamic content, nginx first checks if a cached version exists. If yes, it serves it quickly. If not, it generates the response, caches it briefly, then serves it.

Execution Sample

Nginx

proxy_cache_path /tmp/cache keys_zone=microcache:10m max_size=100m inactive=1m;

server {
  location /dynamic {
    proxy_cache microcache;
    proxy_cache_valid 200 1s;
    proxy_pass http://backend;
  }
}

This config sets up a micro-cache for dynamic content, caching successful responses for 1 second to speed up repeated requests.

Process Table

Step	Action	Cache State	Response Source	Notes
1	Client requests /dynamic	Empty	No cache	First request, cache empty
2	Check cache for /dynamic	Empty	Cache miss	No cached response found
3	Proxy request to backend	Empty	Backend	Request forwarded to backend server
4	Receive response 200 OK	Empty	Backend	Backend sends dynamic content
5	Store response in cache for 1s	Cache has /dynamic	Backend	Response cached briefly
6	Send response to client	Cache has /dynamic	Backend	Client receives fresh content
7	Client requests /dynamic again	Cache has /dynamic	Cache hit	Within 1 second, cache used
8	Serve cached response	Cache has /dynamic	Cache	Fast response from cache
9	Wait 1 second	Cache expires	Cache expired	Cache entry removed after 1s
10	Client requests /dynamic again	Cache empty	Cache miss	Cache expired, new backend request needed

💡 Cache entries expire after 1 second, so repeated requests within that time are served fast from cache.

Status Tracker

Variable	Start	After Step 5	After Step 8	After Step 9	After Step 10
cache_state	Empty	Has /dynamic	Has /dynamic	Expired (Empty)	Empty

Key Moments - 2 Insights

Why does nginx serve from cache on the second request but not the first?

Because at step 2 the cache is empty, so nginx forwards the request to backend (step 3). After receiving the response (step 4), it stores it in cache (step 5). On the second request (step 7), the cache has the response, so nginx serves it directly (step 8).

What happens when the cache expires after 1 second?

At step 9, the cached response expires and is removed. So at step 10, the cache is empty again, causing a cache miss and a new backend request.

Visual Quiz - 3 Questions

Look at the execution table, what is the cache state at step 6?

A Cache has /dynamic

B Cache empty

C Cache expired

D Cache miss

💡 Hint

Refer to the 'Cache State' column at step 6 in the execution table.

At which step does nginx serve the response from cache?

A Step 4

B Step 8

C Step 3

D Step 10

💡 Hint

Check the 'Response Source' column for 'Cache' in the execution table.

If the cache duration was increased to 10 seconds, what would change in the execution table?

A Cache would expire at step 9

B Cache would never expire

C Cache would expire after step 10

D Cache would expire before step 5

💡 Hint

Look at the 'Cache expires' note at step 9 and consider longer cache duration.

Concept Snapshot

Micro-caching in nginx:
- Use proxy_cache_path to define cache storage
- Enable proxy_cache in location block
- Set proxy_cache_valid for short duration (e.g., 1s)
- On request, nginx serves cached response if valid
- Otherwise, fetches from backend and caches it
- Speeds up dynamic content by reducing backend load

Full Transcript

Micro-caching for dynamic content in nginx works by storing responses for a very short time, like 1 second. When a client requests dynamic content, nginx first checks if it has a cached response. If yes, it serves it immediately, making the response faster. If not, it forwards the request to the backend server, gets the response, caches it briefly, and then sends it to the client. This process repeats, so repeated requests within the cache duration are served quickly from cache, reducing backend load. After the cache expires, nginx fetches fresh content again. This technique is useful for dynamic pages that change often but can tolerate very short caching to improve performance.