DRF: per-API-key throttling for B2B customers

# ======================================================================
# Q: How do you throttle per API key for B2B customers?
#
# The cache backend must be shared (Redis), otherwise each worker counts
# separately. It returns 429 with Retry-After.
# ======================================================================

class B2BKeyThrottle(SimpleRateThrottle):
    scope = 'b2b'

    def get_cache_key(self, request, view):
        key = getattr(request.auth, 'key_id', None)
        return self.cache_format % {'scope': self.scope, 'ident': key or self.get_ident(request)}

REST_FRAMEWORK = {
    'DEFAULT_THROTTLE_CLASSES': ['api.throttles.B2BKeyThrottle'],
    'DEFAULT_THROTTLE_RATES': {'b2b': '600/min'},
}