Docker Container Startup Time Calculator
Estimate container cold-start time from image pull, init process and healthcheck delay.
Inputs
Time to pull the image (0 if already cached locally).
Docker API time to create and start the container.
Time for the app process to initialize and be ready to serve.
Interval between healthcheck probes.
Retries allowed during start period before marking healthy.
Cold-Start Time
23.5seconds
Warm-Start Time (cached image)
15.5seconds
Container Ready (before healthcheck)
13.5seconds
Healthcheck Discovery Delay
10seconds
Step by step
Container ready (pull + create + app init)
8s + 0.5s + 5s
= 13.5s
Healthcheck delay (one interval)
10s
= 10s
Total cold-start time
13.5s + 10s
= 23.5s
Warm-start (image cached)
0.5s + 5s + 10s
= 15.5s
How it works
Container startup time = imagePull + createStart + appInit + healthcheckDelay. Cold starts include the image pull; warm starts skip it. The healthcheck interval adds latency between the app being ready and the orchestrator discovering it's healthy.
Formula
Startup Time
startup = imagePull + createStart + appInit + healthcheckInterval
- imagePull
- Image download time (0 if cached)
- createStart
- Docker API overhead
- appInit
- Application initialization time
- healthcheckInterval
- Time until first successful healthcheck
Frequently Asked Questions
How can I reduce cold-start time?
Pre-pull images to nodes, use smaller images (alpine/distroless), optimize application startup (lazy initialization), and reduce healthcheck intervals for faster discovery.
Why does warm start still have healthcheck delay?
Even with a cached image, the orchestrator doesn't route traffic until the healthcheck passes — reducing the interval or using startup probes (in Kubernetes) helps.