Terraform meta argument: depends on

https://www.terraform.io/docs/language/meta-arguments/depends_on.html

The depends_on argument should be used only as a last resort

╷
│ Error: Reference to undeclared resource
│
│   on .terraform/path/to/you/module.tf line 15, in resource "aws_rds_cluster_instance" "this":
│   15:     depends_on = [ "aws_db_subnet_group.this", "aws_rds_cluster.this" ]
│
│ A managed resource "aws_rds_cluster" "this" has not been declared in yourmodule.db.
╵

See also

• Terraform functions, Terraform collection functions: tolist, toset, length, sum, file, join, depends_on, zipmap, replace, lookup, read files, concat, merge, templatefile, for_each, format, element, slice, try, filebase64, upper, filemd5, coalesce
• Terraform, OpenTofu, Installation, Terraform AWS, Terraform GCP, Terraform commands, Terraform Cloud, Terraform Enterprise (TFE), HCL, HIL, meta-arguments, providers, modules, resource, provisioners, data sources, backends: remote backends, examples, configuration files, state files, variables, types, Terraform Registry, conditionals: depends_on, functions, Blocks, dynamic blocks, errors, Terragrunt, Terraformer, Terratest, Terraform certifications, Terraform map type, Terraform Associate, Terraform: list type, TF_VAR_, TF_LOG, Terraform provider versioning, Terraform Style Conventions, Required version, Terraform plugin, Terraform Named Values, tags, Changelog, tfsec, tflint, Operators, Expressions: for, splat, Debugging, Namespaces, Terraform Landing Zones, CDKTF, Atmos