What is Terrantula
Terrantula is the fleet layer that sits above your Terraform. It doesn't run Terraform and it doesn't replace it — it orchestrates the population of infrastructure your Terraform produces.
Pets vs. cattle
Terraform is excellent for pets: long-lived, hand-curated infrastructure you care about individually — the prod cluster, the shared CI account, the data warehouse. Pets get named, version-controlled per-resource, and reviewed line-by-line.
Terraform is awkward for cattle: fleets of templated, often-ephemeral resources where individuals don't matter but the population does — per-tenant stacks, per-PR environments, per-customer databases, cells in a multi-region fleet. Manage cattle with pet-shaped tools and predictable things break: workspace explosion, state proliferation, capacity tribal knowledge, naming collisions, deprovisioning that nobody owns, onboarding that "should take 5 minutes" but takes 4 hours.
Terrantula adds the missing layer. You model the fleet once — typed entities, capacity-bounded cells, cardinality-checked relationships — and Terrantula handles placement, constraint enforcement, lifecycle, and audit across hundreds of instances.
How it actually changes your infrastructure
Terrantula makes changes the way your team already does: by opening a pull request.
When you trigger an Action, Terrantula validates parameters, enforces constraints, picks the right cell, and then opens a PR against your existing repository — committing or patching the IaC files that describe the change. Your CI applies it, exactly as it does today. Terrantula never executes terraform apply itself, and it never hosts your runners or your state.
That single rule is what lets Terrantula sit on top of any substrate: Terraform Cloud, Atmos, Atlantis, OpenTofu, or a bare GitHub Actions workflow with state in S3.
What you see
The dashboard is a read-only projection of state derived from your Terraform. It shows the fleet as a graph — entities, the cells they're placed in, the relationships between them, and the cascade of an in-flight change. You don't edit infrastructure in the UI; every infrastructure change flows through an Action → a PR → your CI. (The UI only writes its own metadata — saved views, pinned positions — and Terrantula-owned intent like cell membership.)
The shortest definition
Terrantula gives you a typed, constraint-enforced, audited view of fleet-shaped infrastructure — and changes it by opening pull requests, not by running Terraform.
Next
- Features — the full capability breadth.
- Use-cases — see the patterns in practice.
- The Cattle Mindset — the longer essay on pets vs. cattle.