Image caches accelerate container startup by eliminating the image pull step. When you launch an Elastic Container Instance (ECI), pulling the container image is the primary contributor to startup time. An image cache stores image data as a snapshot. Instead of pulling the image from a registry, the instance restores directly from the snapshot, cutting startup time significantly.
ECI supports two types of image caches with different billing rules:
| Type | Creation cost | Usage cost |
|---|---|---|
| Manually created image cache | Temporary resources + snapshot storage fee | Disk fee (charged while the instance using the cache runs) |
| Automatically created image cache | Free | Additional temporary storage fee, only if the cache exceeds 30 GiB |
After an image cache is created, you can view its size in the creation event information. For details, see Overview of image caches.
Manually created image caches
Creation billing
When you manually create an image cache, ECI automatically creates a temporary instance (2 vCPUs, 4 GiB memory) with a performance level-1 (PL1) Enterprise SSD (ESSD) attached. The temporary instance pulls the image and builds the cache. After the image cache is created, the temporary instance and disk are automatically released and billing stops.
Two billable items apply during creation:
Temporary resources (temporary instance + temporary disk)
Billed at pay-as-you-go rates for the duration the temporary instance runs. The running duration depends on the image size — larger images take longer to pull.
Creation fee = (vCPU unit price × 2 + memory unit price × 4 + disk unit price × disk capacity) × running duration
Unit prices:
vCPU: USD 0.0000077 per secondUSD 0.00000096/secondUSD 0.0000077/second
Memory: USD 0.00000096 per GiB per second
Disk: see the Storage tab on the
Disk capacity equals the image cache size. For ECI billing rates, see Billing of elastic container instances.
Snapshot storage
Each image cache corresponds to one snapshot. The snapshot persists for as long as you keep the image cache, and its storage fee accrues over that period. For snapshot pricing, see Snapshots.
Usage billing
When you use a manually created image cache to launch an instance, ECI automatically attaches a pay-as-you-go PL1 ESSD to the instance. If a PL1 ESSD is not available, an ultra disk is attached instead. The disk capacity equals the image cache size. The disk is created and released together with the instance. You are charged for the elastic container instance and the disk.
Disk fee = disk unit price × disk capacity × instance running duration
For disk pricing, see Block storage devices.
Automatically created image caches
When you enable automatic image cache matching during instance creation, ECI creates a matching image cache automatically if none exists. Creating the cache automatically is free of charge.
Usage billing
When you use an automatically created image cache to launch an instance, charges depend on the cache size:
| Condition | Billable item |
|---|---|
| Image cache ≤ 30 GiB | No additional charge |
| Image cache > 30 GiB | Additional temporary storage space fee |
If the cache exceeds 30 GiB, you are charged for the additional temporary storage capacity. For pricing, see Temporary storage space.
Billing examples
The following examples are for reference only. Your actual charges may differ from the estimated amounts.
Example 1: Manually created image cache (creation + usage)
Scenario: You create a 40 GiB image cache in the China (Hangzhou) region with the instant image cache feature disabled. The temporary instance runs for 5 minutes (300 seconds) to pull the image. You retain the image cache for 3 days; the corresponding snapshot uses 2 GiB of storage. You then use the image cache to launch an instance that runs for 3 hours.
Creation cost
Temporary resource fee:
(0.0000077 × 2 + 0.00000096 × 4 + 0.05/100/3,600 × 40) × 300 = USD 0.007449Snapshot storage fee (3 days):
0.02/30 × 2 × 3 = USD 0.004Total creation cost: USD 0.007449 + USD 0.004 = USD 0.011449USD 0.007449 + USD 0.004 = USD 0.011449
Usage cost
Disk fee (instance running for 3 hours):
0.05/100 × 40 × 3 = USD 0.06Example 2: Automatically created image cache
Scenario: You create Elastic Container Instance A in the China (Hangzhou) region using an image that is 30 GiB or smaller. You enable automatic image cache matching. Because no existing cache matches, ECI automatically creates one — at no charge.
When you later launch Elastic Container Instance B from that image cache, you are charged only for the instance itself. No additional disk or cache fee applies because the cache does not exceed 30 GiB.