Drag a database onto the canvas.
It actually runs.
Torollo is a free, local-first system design lab. Every node you drop becomes a real Docker container on your machine, with a real shell and real networking. Guided roadmaps grade each step against the live state of those containers.
MIT licensed · runs entirely on your machine · Docker required
Validate → ✗ "port 5432 is still open from lb to db" → fix the security group → Validate → ✓ → roadmap complete. No mocks: every verdict comes from the backend inspecting the containers.
The way to learn a load balancer is to run one, break it, and read the logs it writes while it fails.
build
A canvas that provisions
Drop Postgres, Redis, an nginx load balancer, subnets, NAT, security groups. Each card is a container created on your machine the moment it lands. The IP on the card is the container’s actual IP, and the subnet border is a real Docker network.
run
Every node opens a shell
The terminal on each node is docker exec into that container. Query Postgres from the built-in explorer or from psql, ping Redis, curl your load balancer, and set CPU and memory limits per container.
break
Checks that inspect your containers
A roadmap step is graded by inspecting the live state of your containers. When a check fails, it tells you what it looked at and what it found instead. You pass by changing the architecture until the check observes what it expects.
prove
Every pass leaves a receipt
A validation pass produces a list of observations made against your machine. This is the receipt for step 7 of the three-tier roadmap.
check: container "web-1" is running
check: container "db" is running
check: table "users" exists in "db"
check: web-1 → db is reachable on :5432
check: lb → db is blocked on :5432
✓ step 7 of 10 · validation passed
Three roadmaps ship free
They tell one continuing story: you are the first engineer at a bookstore that keeps outgrowing its architecture. Every step is validated against your containers.
10 steps · ~40 min · intermediate
Deploy a resilient three-tier app
Nimbus Books is about to launch. Build the classic three tiers on real containers, lock them down, then break the setup on purpose and watch it survive.
read the full brief →
9 steps · ~45 min · intermediate
Cache-aside with Redis
Launch day went too well: every page load hammers Postgres with the same catalog query. Put Redis in front of it and prove the hit rate.
read the full brief →
8 steps · ~40 min · intermediate
Workers & the Redis job queue
Checkout freezes for two full seconds while each receipt renders. Move the work behind a queue and let workers drain it.
read the full brief →
The roadmap format is open JSON. Write your own and the validator runs it. Read the format spec. Beyond the free catalogue, advanced scenario packs live on the pricing page.
What runs underneath the canvas
Local-first
Projects live in ~/.torollo and containers run on your local Docker daemon. Apart from pulling Docker images, the app makes no network calls unless you opt into telemetry.
MIT licensed, engine and format
The canvas, the Docker runtime, the network engine, the terminals, the validator and the roadmap format are all open source. Every node type is included; there is no paid tier of nodes.
Real networking
Subnets become Docker bridge networks. Security groups become iptables rules inside the containers. NAT gateways apply a real MASQUERADE rule.
Boot your first architecture in two minutes.
The only requirement is a running Docker daemon. There is no account to create and no cloud to configure.