What is Django LocMemCache (Local Memory Cache)?

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LocMemCache is Django’s local‑memory cache backend. If you don’t configure a cache, Django falls back to this local memory cache by default. It’s handy for lightweight apps that don’t need shared memory, or for quickly testing on a development server before setting up Redis.

Key points

  • Storage location: RAM of the currently running Django process
  • Scope: Per‑process – not shared outside the process
  • Thread‑safety: Thread‑safe

What problems does it solve?

A cache temporarily holds expensive calculations or queries so they can be reused on subsequent requests.

For example, if you cache a frequently queried value from the database:

  • First request: query DB → store result in cache
  • Subsequent requests: return immediately from cache (fast)

LocMemCache stores this cache directly in your process’s memory without any external system like Redis or Memcached.

Core operation details

1) It’s a per‑process cache (most important)

The Django docs state clearly: the local memory cache is per‑process. That means:

  • With 4 Gunicorn workers → 4 separate caches
  • With 2 servers → each server has its own cache

So caches are not shared across processes or servers.

2) It’s thread‑safe

The backend is designed to be safe when multiple threads in the same process access it concurrently.

3) It disappears on restart

Because it lives only in memory, restarting the process clears the cache.

How to configure it

Add the following to settings.py under CACHES:

CACHES = {
    "default": {
        "BACKEND": "django.core.cache.backends.locmem.LocMemCache",
        "LOCATION": "unique-snowflake",
    }
}

The example from the official docs uses this format; LOCATION simply identifies the cache instance.

Advantages

  • Minimal setup – no external cache server needed
  • Fast – access to the same process’s memory incurs very low latency
  • Convenient for development/testing – great for adding caching concepts without external dependencies

Drawbacks and cautions

  • Cache fragmentation in multi‑process/multi‑server setups – you may see “cache not working” because each process has its own cache
  • Unpredictable in production – traffic spread across many processes can lower hit rates
  • Not recommended for session storage – Django’s session docs warn that local memory caches don’t persist long enough and aren’t safe across multiple processes

When is it appropriate to use?

  • Local development environments
  • Single‑process deployments (or when cache sharing isn’t required)
  • Feature validation/testing with minimal external dependencies

If you need the same cache across multiple processes or servers, it’s usually better to use a shared cache like Redis or Memcached.