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Prebuilt workspaces

Prebuilt workspaces (prebuilds) reduce workspace creation time with an automatically-maintained pool of ready-to-use workspaces for specific parameter presets.

The template administrator defines the prebuilt workspace's parameters and number of instances to keep provisioned. The desired number of workspaces are then provisioned transparently. When a developer creates a new workspace that matches the definition, Coder assigns them an existing prebuilt workspace. This significantly reduces wait times, especially for templates with complex provisioning or lengthy startup procedures.

Prebuilt workspaces are:

Created and maintained automatically by Coder to match your specified preset configurations.
Claimed transparently when developers create workspaces.
Monitored and replaced automatically to maintain your desired pool size.
Automatically scaled based on time-based schedules to optimize resource usage.

Prebuilt workspaces are a special type of workspace that don't follow the regular workspace scheduling features like autostart and autostop. Instead, they have their own reconciliation loop that handles prebuild-specific scheduling features such as TTL and prebuild scheduling.

Relationship to workspace presets

Prebuilt workspaces are tightly integrated with workspace presets:

Each prebuilt workspace is associated with a specific template preset.
The preset must define all required parameters needed to build the workspace.
The preset parameters define the base configuration and are immutable once a prebuilt workspace is provisioned.
Parameters that are not defined in the preset can still be customized by users when they claim a workspace.
If a user does not select a preset but provides parameters that match one or more presets, Coder will automatically select the most specific matching preset and assign a prebuilt workspace if one is available.

Prerequisites

Premium license
Compatible Terraform provider: Use coder/coder Terraform provider >= 2.4.1.

Enable prebuilt workspaces for template presets

In your template, add a prebuilds block within a coder_workspace_preset definition to identify the number of prebuilt instances your Coder deployment should maintain, and optionally configure a expiration_policy block to set a TTL (Time To Live) for unclaimed prebuilt workspaces to ensure stale resources are automatically cleaned up.

data "coder_workspace_preset" "goland" {
  name = "GoLand: Large"
  parameters = {
    jetbrains_ide = "GO"
    cpus          = 8
    memory        = 16
  }
  prebuilds {
    instances = 3   # Number of prebuilt workspaces to maintain
    expiration_policy {
       ttl = 86400  # Time (in seconds) after which unclaimed prebuilds are expired (86400 = 1 day)
   }
  }
}

After you publish a new template version, Coder will automatically provision and maintain prebuilt workspaces through an internal reconciliation loop (similar to Kubernetes) to ensure the defined instances count are running.

The expiration_policy block ensures that any prebuilt workspaces left unclaimed for more than ttl seconds is considered expired and automatically cleaned up.

Prebuilt workspace lifecycle

Prebuilt workspaces follow a specific lifecycle from creation through eligibility to claiming.

After you configure a preset with prebuilds and publish the template, Coder provisions the prebuilt workspace(s).
1. Coder automatically creates the defined instances count of prebuilt workspaces.
2. Each new prebuilt workspace is initially owned by an unprivileged system pseudo-user named prebuilds.
  - The prebuilds user belongs to the Everyone group (you can add it to additional groups if needed).
3. Each prebuilt workspace receives a randomly generated name for identification.
4. The workspace is provisioned like a regular workspace; only its ownership distinguishes it as a prebuilt workspace.
Prebuilt workspaces start up and become eligible to be claimed by a developer.

Before a prebuilt workspace is available to users:
1. The workspace is provisioned.
2. The agent starts up and connects to coderd.
3. The agent starts its bootstrap procedures and completes its startup scripts.
4. The agent reports ready status.
  
  After the agent reports ready, the prebuilt workspace considered eligible to be claimed.
Prebuilt workspaces that fail during provisioning are retried with a backoff to prevent transient failures.
When a developer creates a new workspace, the claiming process occurs:
1. Developer selects a template and preset that has prebuilt workspaces configured.
2. If an eligible prebuilt workspace exists, ownership transfers from the prebuilds user to the requesting user.
3. The workspace name changes to the user's requested name.
4. terraform apply is executed using the new ownership details, which may affect the coder_workspace and coder_workspace_owner datasources (see Preventing resource replacement for further considerations).
The claiming process is transparent to the developer — the workspace will just be ready faster than usual.

You can view available prebuilt workspaces in the Workspaces view in the Coder dashboard:

Note the search term owner:prebuilds.

Unclaimed prebuilt workspaces can be interacted with in the same way as any other workspace. However, if a Prebuilt workspace is stopped, the reconciliation loop will not destroy it. This gives template admins the ability to park problematic prebuilt workspaces in a stopped state for further investigation.

Expiration Policy

Prebuilt workspaces support expiration policies through the ttl setting inside the expiration_policy block. This value defines the Time To Live (TTL) of a prebuilt workspace, i.e., the duration in seconds that an unclaimed prebuilt workspace can remain before it is considered expired and eligible for cleanup.

Expired prebuilt workspaces are removed during the reconciliation loop to avoid stale environments and resource waste. New prebuilt workspaces are only created to maintain the desired count if needed.

Scheduling

Prebuilt workspaces support time-based scheduling to scale the number of instances up or down. This allows you to reduce resource costs during off-hours while maintaining availability during peak usage times.

Configure scheduling by adding a scheduling block within your prebuilds configuration:

data "coder_workspace_preset" "goland" {
   name = "GoLand: Large"
   parameters {
     jetbrains_ide = "GO"
     cpus          = 8
     memory        = 16
   }

   prebuilds {
     instances = 0                  # default to 0 instances

     scheduling {
       timezone = "UTC"             # only a single timezone may be used for simplicity

       # scale to 3 instances during the work week
       schedule {
         cron = "* 8-18 * * 1-5"    # from 8AM-6:59PM, Mon-Fri, UTC
         instances = 3              # scale to 3 instances
       }

       # scale to 1 instance on Saturdays for urgent support queries
       schedule {
         cron = "* 8-14 * * 6"      # from 8AM-2:59PM, Sat, UTC
         instances = 1              # scale to 1 instance
       }
     }
   }
}

Scheduling configuration:

timezone: (Required) The timezone for all cron expressions. Only a single timezone is supported per scheduling configuration.
schedule: One or more schedule blocks defining when to scale to specific instance counts.
- cron: (Required) Cron expression interpreted as continuous time ranges.
- instances: (Required) Number of prebuilt workspaces to maintain during this schedule.

How scheduling works:

The reconciliation loop evaluates all active schedules every reconciliation interval (CODER_WORKSPACE_PREBUILDS_RECONCILIATION_INTERVAL).
The schedule that matches the current time becomes active. Overlapping schedules are disallowed by validation rules.
If no schedules match the current time, the base instances count is used.
The reconciliation loop automatically creates or destroys prebuilt workspaces to match the target count.

Cron expression format:

Cron expressions follow the format: * HOUR DOM MONTH DAY-OF-WEEK

* (minute): Must always be * to ensure the schedule covers entire hours rather than specific minute intervals
HOUR: 0-23, range (e.g., 8-18 for 8AM-6:59PM), or *
DOM (day-of-month): 1-31, range, or *
MONTH: 1-12, range, or *
DAY-OF-WEEK: 0-6 (Sunday=0, Saturday=6), range (e.g., 1-5 for Monday to Friday), or *

Important notes about cron expressions:

Minutes must always be *: To ensure the schedule covers entire hours
Time ranges are continuous: A range like 8-18 means from 8AM to 6:59PM (inclusive of both start and end hours)
Weekday ranges: 1-5 means Monday through Friday (Monday=1, Friday=5)
No overlapping schedules: The validation system prevents overlapping schedules.

Example schedules:

# Business hours only (8AM-6:59PM, Mon-Fri)
schedule {
  cron = "* 8-18 * * 1-5"
  instances = 5
}

# 24/7 coverage with reduced capacity overnight and on weekends
schedule {
  cron = "* 8-18 * * 1-5"  # Business hours (8AM-6:59PM, Mon-Fri)
  instances = 10
}
schedule {
  cron = "* 19-23,0-7 * * 1,5"  # Evenings and nights (7PM-11:59PM, 12AM-7:59AM, Mon-Fri)
  instances = 2
}
schedule {
  cron = "* * * * 6,0"  # Weekends
  instances = 2
}

# Weekend support (10AM-4:59PM, Sat-Sun)
schedule {
  cron = "* 10-16 * * 6,0"
  instances = 1
}

Template updates and the prebuilt workspace lifecycle

Prebuilt workspaces are not updated after they are provisioned.

When a template's active version is updated:

Prebuilt workspaces for old versions are automatically deleted.
New prebuilt workspaces are created for the active template version.
If dependencies change (e.g., an AMI update) without a template version change:
- You can delete the existing prebuilt workspaces manually.
- Coder will automatically create new prebuilt workspaces with the updated dependencies.

The system always maintains the desired number of prebuilt workspaces for the active template version.

Administration and troubleshooting

Managing resource quotas

To help prevent unexpected infrastructure costs, prebuilt workspaces can be used in conjunction with resource quotas. Because unclaimed prebuilt workspaces are owned by the prebuilds user, you can:

Configure quotas for any group that includes this user.
Set appropriate limits to balance prebuilt workspace availability with resource constraints.

When prebuilt workspaces are configured for an organization, Coder creates a "prebuilds" group in that organization and adds the prebuilds user to it. This group has a default quota allowance of 0, which you should adjust based on your needs:

Set a quota allowance on the "prebuilds" group to control how many prebuilt workspaces can be provisioned
Monitor usage to ensure the quota is appropriate for your desired number of prebuilt instances
Adjust as needed based on your template costs and desired prebuilt workspace pool size

If a quota is exceeded, the prebuilt workspace will fail provisioning the same way other workspaces do.

Template configuration best practices

Preventing resource replacement

When a prebuilt workspace is claimed, another terraform apply run occurs with new values for the workspace owner and name.

This can cause issues in the following scenario:

The workspace is initially created with values from the prebuilds user and a random name.
After claiming, various workspace properties change (ownership, name, and potentially other values), which Terraform sees as configuration drift.
If these values are used in immutable fields, Terraform will destroy and recreate the resource, eliminating the benefit of prebuilds.

For example, when these values are used in immutable fields like the AWS instance user_data, you'll see resource replacement during claiming:

To prevent this, add a lifecycle block with ignore_changes:

resource "docker_container" "workspace" {
  lifecycle {
    ignore_changes = [env, image] # include all fields which caused drift
  }

  count = data.coder_workspace.me.start_count
  name  = "coder-${data.coder_workspace_owner.me.name}-${lower(data.coder_workspace.me.name)}"
  ...
}

Limit the scope of ignore_changes to include only the fields specified in the notification. If you include too many fields, Terraform might ignore changes that wouldn't otherwise cause drift.

Learn more about ignore_changes in the Terraform documentation.

A note on "immutable" attributes: Terraform providers may specify ForceNew on their resources' attributes. Any change to these attributes require the replacement (destruction and recreation) of the managed resource instance, rather than an in-place update. For example, the ami attribute on the aws_instance resource has ForceNew set, since the AMI cannot be changed in-place.

Monitoring and observability

Available metrics

Coder provides several metrics to monitor your prebuilt workspaces:

coderd_prebuilt_workspaces_created_total (counter): Total number of prebuilt workspaces created to meet the desired instance count.
coderd_prebuilt_workspaces_failed_total (counter): Total number of prebuilt workspaces that failed to build.
coderd_prebuilt_workspaces_claimed_total (counter): Total number of prebuilt workspaces claimed by users.
coderd_prebuilt_workspaces_desired (gauge): Target number of prebuilt workspaces that should be available.
coderd_prebuilt_workspaces_running (gauge): Current number of prebuilt workspaces in a running state.
coderd_prebuilt_workspaces_eligible (gauge): Current number of prebuilt workspaces eligible to be claimed.
coderd_prebuilt_workspace_claim_duration_seconds (native histogram support): Time to claim a prebuilt workspace from the prebuild pool.

Logs

Search for coderd.prebuilds: in your logs to track the reconciliation loop's behavior.

These logs provide information about:

Creation and deletion attempts for prebuilt workspaces.
Backoff events after failed builds.
Claiming operations.