How does Terraform State Locking work?

Question

Accepted Answer

**State Locking** — Prevents concurrent modifications to the state file.

**S3 + DynamoDB:**
```hcl
terraform {
  backend "s3" {
    bucket         = "my-terraform-state"
    key            = "prod/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "terraform-locks"
    encrypt        = true
  }
}
```

**How DynamoDB lock works:**
1. Terraform creates an entry in DynamoDB with a lock ID.
2. Another user sees that the lock is occupied.
3. After apply — the lock is released.

**Manual management:**
```bash
terraform force-unlock LOCK_ID
```

**Alternatives:** Consul, Azure Blob Storage, Terraform Cloud.

**Best practice:** Always use a remote backend with locking.

DevOps: How does Terraform State Locking work?