Variant Expiration

Variant expiration controls how long cached variants are retained in your object store before Konifer treats them as expired and purges them. Expiration applies to both eager and on-demand variants.

Expiration is configured in Path Configuration using transform.expire. Since path configuration is inherited, expiration rules defined on a parent path apply to child paths unless they are overridden by a more-specific path.

paths {
  "/**" {
    transform {
      expire {
        strategy = ttl
        ttl = 7d
      }
    }
  }

  "/users/**" {
    transform {
      expire {
        ttl = 30d
      }
    }
  }
}

In this example, all variants expire after 7 days by default, but variants under /users/** expire after 30 days. Both strategy and ttl can be overridden by a more-specific path.

Expiration Strategies

Konifer supports three expiration strategies:

• never: Variants do not expire.
• ttl: Variants expire after a fixed amount of time since they were created.
• idle: Variants expire after a fixed amount of time since they were last accessed.

The ttl property is used by both ttl and idle strategies and is ignored when the strategy is never.

ttl

The ttl strategy expires a variant after a fixed lifetime measured from the time the variant is generated and cached. Accessing the variant does not extend its lifetime.

This strategy is useful when you want a predictable maximum lifetime for cached variants regardless of how frequently they are requested.

idle

The idle strategy also uses ttl, but the timer is based on the variant's last access time rather than its creation time. Each successful access refreshes the expiration window.

This strategy is useful when you want frequently requested variants to remain cached while allowing unused variants to age out automatically.

Eager and On-demand Variants

Eager and on-demand variants follow the same expiration rules. The difference is when the variant is first created.

An on-demand variant is generated at the time of its first request, so its creation time and first access time are the same.

An eager variant may be generated before it is ever requested. That distinction does not change behavior under the never or ttl strategies, but it can matter under idle. Since idle is based on the last access time, an eager variant that is generated but never requested may expire without ever being served.

Duration Format

The ttl value uses Konifer's standard Duration format. For example:

• 10m
• 24h
• 7d

See the Path Configuration Reference for the complete property reference.

note

Due to how expired variants are purged, expiration may be delayed by up to 1 minute after the configured TTL.