Compute resource limits
Last updated 2025-04-22
This guide details Fastly resource limits for Compute services. These limits change based on whether or not you've purchased one of our packaged offerings or you're using a trial account.
NOTE
In addition to the limits described here, Compute services can also be limited by the products or platform services that you access through your application code. Check out our network services resource limits for additional details.
Port limits
Compute services accept client connections on port 443 only. This is different from VCL services, which support client connections on port 80.
NOTE
If your Compute service receives a request on port 80, Fastly automatically returns a 308 Permanent Redirect response status with the Location header indicating the HTTPS version of the same URL in a Location header.
Default limits
| Item | Limit | Scope |
|---|---|---|
| Maximum compiled package size | 100MB | per service |
| Maximum cached object size | 100MB | per object |
| Maximum CPU time available to a single request instance | 50ms | per execution |
| Maximum runtime for a single request instance | 2 min (60s for trial accounts) | per execution |
| Maximum memory consumption | 1M bytes stack, 128MB heap | per execution |
| Maximum number of dictionary lookups | 16 | per execution |
| Maximum number of backend requests | 32 (10 for trial accounts) | per execution |
| Maximum number of dynamic backends | 200 | per service |
| Vary rules | 8 | per cache object |
| Maximum length of a request header | 128KB | per header |
| Maximum length of a response header | 128KB | per header |
| Maximum length of a method name | 8192 bytes | per request |
| Maximum length of a URL | 8192 bytes | per request |
An execution refers to a single instance of a Compute program being executed, normally in response to a client HTTP request. Separate limits also apply to the use of log tailing with Compute services.
Service chain limits
| Item | Limit | Implications |
|---|---|---|
| Service chains and hops | 20 hops, 6 unique services | Read our developer information about loop detection for more info. |
Edge data storage limits
Limits for each of our edge data storage options differ if you've purchased a package offering or are using a product or feature trial.
Config Store
Config Store is included with your Compute service with the following limitations.
| Item | Trial limit | Paid account limit | Implications |
|---|---|---|---|
| Config stores | 1 | 5 | Paid accounts can purchase additional stores for a monthly fee. |
| Config store entries (per store) | 100 | 500 | An error informs you that you've exceeded the limit. |
| Config store key length | 255 characters | 255 characters | An error informs you that you've exceeded the limit. |
| Config store value length | 8,000 characters | 8,000 characters | An error informs you that you've exceeded the limit. |
| Config store write operations | 100 writes per hour | 100 writes per hour | Write limits are shared with all other Fastly API calls. Exceeding the limit will result in an API limit error. Refer to API rate limiting for more info. |
KV Store
KV Store is an add-on and is priced in addition to Compute services. The number of KV Stores is limited to the account’s available resources allotment. The following limitations also apply:
- Values stored in KV Store items are limited by default to 25MB, but that limit can be raised to as much as 100MB upon request. Contact your account manager or sales@fastly.com for more information.
- Metadata stored in KV Store items is limited to 2000 bytes and must be composed of Unicode characters encoded using UTF-8.
- KV Stores have a rate limit of 1,000 writes per second per store, and 5,000 reads per second per store. These are soft limits for the durable store and they auto-scale as needed.
- KV Store items have a rate limit of 1 write per second per item.
- KV Store item batch requests have a limit of 100,000 items per request.
- KV Stores provide eventual consistency, which means that reading a key immediately after writing it may not return the updated value.
Store name limitations
- KV store names must begin with an ASCII alphabetical character and must be composed of Unicode characters encoded using UTF-8.
- Store names cannot contain Unicode control characters.
- Store names are limited to 255 bytes.
Key limitations
- Keys cannot start with
.well-known/acme-challenge/,., or... - Key names can contain any sequence of valid Unicode characters of length 1-1024 bytes when UTF-8 encoded. The following characters can be used in key names but can't be searched in a prefix query string:
!,",$,%,&,(,),*,+,,,/,\,:,<,=,>,@,[,],`,{,}. - Keys cannot use Unicode characters 0 through 32, 65534, and 65535 as single-character key names.
- The following characters cannot be used in key names:
#,;,?,^, and|- line feed (LF) characters
- carriage-return (CR) characters
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