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Resource limits

  Last updated July 16, 2018

This guide details Fastly resource limits and summarizes the implications of exceeding those limits.

Cache limits

Item Limit Implications
Cache file size (with streaming miss) 5GB Exceeding this limit when trying to cache an object results in a Service unavailable error.
Cache file size (without streaming miss) 2GB Exceeding this limit when trying to cache an object results in a Service unavailable error.
Vary objects count 200 Exceeding the limit results in no error. Newer variants displace the oldest.

Rate and time limits

Item Limit Implications
API rate limit 1000 requests/hour Exceeding this limit results in a Too many requests error. This limit applies to non-read requests per user, not per token. See API rate limiting for more info.
TLS connections limit 10 minutes Exceeding this limit results in a 502 gateway timeout error.

Request and header limits

Item Limit Implications
URL size 8KB Exceeding the limit results in a Too long request string error.
Cookie size 32KB Exceeding the limit results in a CookieOverflow error.
Header size 69KB Exceeding the limit results in a 503 backend read error. See Common 503 errors for more info.
Header count 96 Exceeding the limit results in a Header overflow error. A small portion of this limit is reserved for internal Fastly use, making the practical limit closer to 85.
Surrogate key size 1KB Exceeding the limit results in purging API failures stating "surrogate key too long, must be less than 1024 bytes." Any keys that exceed the limit will be dropped instead of truncated.
Surrogate key header size 16KB Exceeding the limit results in no error and any keys past the one that exceeds the limit will be dropped.

Service, domain, and origin limits

Item Limit Implications
Services total per account 10 Exceeding this limit results in an Exceeding max_total_services error. Contact support@fastly.com to discuss raising this limit.
Origins per service 5 Exceeding this limit results in an Exceeding max_backends error. Contact support@fastly.com to discuss raising this limit.
Domains per service 20 Exceeding this limit results in an Exceeding max number of domains error. Contact support@fastly.com to discuss raising this limit.
Connections per service 200 Exceeding this limit results in an Error 503 backend.max_conn reached error. You can increase this limit as high as 1000 by updating the backend connection setting to limit the connections a single Fastly cache server will make to a specific origin server.

VCL and configuration limits

Item Limit Implications
Custom VCL file size 1MB Exceeding the limit results in a Content too long error.
Edge dictionary items count 1000 Exceeding the limit results in an Exceeding max dictionary items error. Contact support@fastly.com to discuss raising this limit.
Edge dictionary item key length 256 characters Exceeding the limit results in an Item key is too long error.
Edge dictionary item value length 8000 characters Exceeding the limit results in an Item value cannot be greater than error.

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