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Reference

    Resource limits

      Last updated October 03, 2019

    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 unless Segmented Caching is enabled.
    Cache file size (without streaming miss) 2GB Exceeding this limit when trying to cache an object results in a Service unavailable error unless Segmented Caching is enabled.
    Vary objects count 200 soft, 400 hard Exceeding the soft limit results in no error. Newer variants displace the oldest. Active fetches from backends are limited to 400 variants. Exceeding this hard limit results in a Too many variants response. Once fetches complete, objects will be removed until the soft limit is reached.

    Rate and time limits

    Item Limit Implications
    API rate limit 1000 requests/hour Exceeding this limit results in a Too many requests error. The limit is applied to the authenticated user making the request. 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 Fastly stripping the cookie and setting req.http.Fastly-Cookie-Overflow = "1".
    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.
    req.body size 8KB Exceeding the limit results in the req.body variable being blank. Request body payload is available in req.body only for payloads smaller than 8KB. req.postbody is an alias for req.body.
    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.
    Varnish restart limit 3 restarts Exceeding the limit results in a Service Unavailable error. This limit exists to prevent infinite loops.
    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.
    Synthetic response characters No character limit Synthetic responses have no character limit, but large responses may trigger an error for the custom VCL file size limit.
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