Nginx: Protecting upstream from overload on cache miss

These 2 magical lines will protect your upstream server from possible overload of many users try to access the same in cached or expired content: 

proxy_cache_use_stale updating timeout; # Serve the cached version even when outdated while refreshing it proxy_cache_lock on; # Only one req is allowed to load/refresh the item, others wait / get the stale one 

You can verify this using Shopify's Toxiproxy. 

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