Atlas: manage clusters, users, and network as Terraform code

TL;DR: The MongoDB Atlas Terraform provider owns the control plane: project, cluster, database user, IP list, backup policy. One apply, reviewed in a PR. Verify plan shows no changes after apply (converged), and the Atlas UI reflects the resources.

Terraform with the mongodbatlas provider

provider "mongodbatlas" {
  public_key [your value]
  private_key value var.atlas_private_key
}

resource "mongodbatlas_project" "main" {
  name   = "production"
  org_id = var.org_id
}

resource "mongodbatlas_cluster" "main" {
  project_id   = mongodbatlas_project.main.id
  name         = "prod"
  cluster_type = "REPLICASET"
  provider_name = "AWS"
  provider_region_name = "US_EAST_1"
  provider_instance_size_name = "M10"
}

resource "mongodbatlas_database_user" "app" {
  project_id         = mongodbatlas_project.main.id
  username           = "app-svc"
  password value var.db_password
  auth_database_name = "admin"
  roles { role_name = "readWrite" database_name = "mydb" }
}

resource "mongodbatlas_project_ip_access_list" "office" {
  project_id = mongodbatlas_project.main.id
  cidr_block = "203.0.113.0/24"
  comment    = "office egress"
}

Rules

• Pin the provider version. Provider upgrades change resource schemas.
• API keys for Terraform need project-level permissions; scope them to the one project and keep them out of the repo (env vars or a secret store).
• terraform plan in CI on every PR; apply only from the main branch. Control-plane changes deserve the same review as code.
• Import existing manually-created resources before managing them, or Terraform will try to recreate your cluster.

Verify

plan shows no changes after apply (converged), and the Atlas UI reflects the resources. Then make one small change through a PR to prove the whole loop.

When to use this

• This covers exactly what the title says: Atlas.
• You are setting this up for the first time, or auditing an existing setup.
• You want the key gotchas in one place before you start.

When not to use this

• You are doing a different workflow with Atlas; these steps are specific to the title above.
• You need the full reference docs; this is the short path, not the manual.

Terraform MongoDB Atlas provider resources (project, cluster, databaseuser, projectipaccesslist) per the provider documentation; Atlas project and cluster concepts per https://www.mongodb.com/docs/atlas/manage-flex-clusters/, verified 2026-09-26.