Caching

Pick a backend in .env. Memory is fine while you’re developing; Redis is what you want once more than one process is serving requests.

.env

CACHE_BACKEND=memory       # in-memory, single process, cleared on restart
# or
CACHE_BACKEND=redis        # shared across processes, persistent
CACHE_URL=redis://localhost:6379/0
CACHE_DEFAULT_TTL=300      # seconds

CACHE_URL defaults to REDIS_URL. When CACHE_BACKEND is unset, REDIS_URL selects redis. See automatic backends.

Caching function results

Results are keyed by the function’s arguments, so each distinct call gets its own entry.

from feather import cached

@cached(ttl=60)
def get_user_stats(user_id):
    return calculate_stats(user_id)

stats = get_user_stats(123)   # first call executes
stats = get_user_stats(123)   # second call returns the cached value

get_user_stats.invalidate(user_id=123)   # invalidate when data changes

Caching route responses

from feather import cache_response

@api.get('/products')
@cache_response(ttl=300)
def list_products():
    return {'products': Product.query.all()}

# custom cache key from URL params
@api.get('/users/<user_id>')
@cache_response(ttl=60, key='user:{user_id}')
def get_user(user_id):
    return {'user': User.query.get(user_id)}

# skip the cache conditionally
@api.get('/dashboard')
@cache_response(ttl=300, unless=lambda: current_user.is_admin)
def dashboard():
    return {'stats': get_stats()}

cache_response varies on the current user by default. On a genuinely public page pass vary_on_user=False, or every visitor stores a separate copy of an identical response.

Direct access

from feather import get_cache

cache = get_cache()
cache.set('key', {'data': 'value'}, ttl=60)
value = cache.get('key')      # None if expired or missing
cache.delete('key')

The memory backend is per-process. Under gunicorn --workers 4 each worker keeps its own cache, so hit rates look worse than they are and invalidation reaches one worker only. Use redis whenever you run more than one process.

Get started

Tutorial: build a Kanban app

Building the UI

Backend

Features

Tooling

Testing

Deployment

Caching function results

Caching route responses

Direct access

​Caching function results

​Caching route responses

​Direct access

Caching function results

Caching route responses

Direct access