Tools for your real work, with the lesson behind each one

SQL Lab

Real PostgreSQL in your browser for the queries work needs: month-end reports, retention, data-quality checks and schema design, on your own CSV or schema or on sample databases from your industry. Read plans and time indexes too.

For: DBA · Backend developer · Data analyst · Business analyst

Templates for real work: Monthly sales report · Cohort retention · Data-quality checks · Schema design for a new feature

SQL Basics (free) · Fix the slow report · Data detective · Loyalty analytics

Code Lab

Write, run and test the small programs work needs: scripts, API clients with retries, CSV cleaners and tests. JavaScript, TypeScript and Python in a sandbox, React previews in a phone frame.

For: Developer · QA engineer · Mobile developer · Vibe coder

Templates for real work: Utility script · API client with retries · CSV cleaner · Unit-test starter

JS Basics (free) · Async puzzles · Refactor kata · Checkout engine

System Design Studio

Draw the system you run or plan, size every part and push real traffic through it: architecture reviews, capacity plans and post-mortem diagrams you can export as pictures. Challenge campaigns and daily incident drills too.

For: Architect · Backend developer · SRE · Product manager

Templates for real work: Architecture review · Capacity plan · Incident post-mortem diagram

Fundamentals (free) · URL shortener · Video platform · Payments at scale · Route through the app · Courier dispatch · Live scores at peak · Incident drills (daily drill free)

Design challenges (Fundamentals free)Incident drills (daily drill free)

Data Lab

A Python notebook with pandas and charts on your own CSV files or the sample databases: weekly KPI dashboards, A/B test readouts and forecasts, exported as Jupyter notebooks, CSV and charts.

For: Data analyst · Data scientist

Templates for real work: KPI dashboard notebook · A/B test readout · Simple forecast

Notebook basics (free) · Find the trend · Forecast the festival week

Finance Lab

A spreadsheet in your browser with a safe formula engine, several sheets and scenario sliders, plus templates for everyday decisions: budgets, unit economics, LTV/CAC, break-even, cash flow, NPV/IRR, DCF, cloud costs and pricing.

For: Finance · Founder · Product manager · Engineering manager

Templates for real work: Monthly budget against actual · Unit economics of an order · Break-even for a new site · LTV and CAC · 12-month cash-flow forecast · Loan payments · NPV and IRR business case · Cloud cost model · Pricing calculator · Simple DCF

Finance basics (free)

Product & BA Lab

The documents product managers and business analysts write every week: PRDs, sprint plans against real capacity, roadmaps, RICE and MoSCoW, metric trees, story maps, swimlane process maps with a validator and a traceability matrix. Check them against your own criteria and export them.

For: Product manager · Business analyst · Business architect · Product owner

Templates for real work: PRD for a new feature · Sprint plan · Process map: as-is and to-be · Backlog prioritisation (RICE and MoSCoW) · Requirements traceability matrix

Product basics (free)

Learn the ideas: Business Analysis (course)From Spec to Launch (course)

Security Lab

Defensive security work in a sandbox: threat-model checklists, password policies as tested code and sign-in log triage, plus case studies where you patch a deliberately vulnerable Mangrove mini-app and prove the attack stops working. Everything runs locally against fake data.

For: Security engineer (defence) · Security engineer (offence) · Backend developer

Templates for real work: Threat model checklist · Password policy checker · Log triage

Patch the basics (free) · Defender's desk · Harden the handler · Session hardening

QA Lab

Test plans, regression suites and bug reports as code that checks itself, case studies with real bugs to find and fix, and mutation-testing campaigns that score your tests by the hidden bugs they catch.

For: QA engineer · Developer

Templates for real work: Test plan · Regression suite · Bug-report template

Kill the mutants (free) · The receipt printer

DevOps & TechOps Lab

A CI/CD pipeline builder you can run, runbooks and release checklists you tick as you work, a simulated Linux terminal with git, and an incident console. Export pipelines as YAML and runbooks as Markdown.

For: DevOps engineer · SRE · TechOps

Templates for real work: Release checklist · Runbook · Pipeline template

First commands (free) · Fix the broken pipeline · Night shift on-call · Zero-downtime deploy

AI Lab

Tools for everyday AI work that need no model: a prompt builder with a linter, eval sets scored on outputs you paste from any chatbot, a JSON Schema checker, RAG chunking, an agent flow designer, and token and cost estimates. Optionally run a small model on your own device, free.

For: AI engineer · Developer · Product manager · Vibe coder

Templates for real work: Prompt review · Eval set for a chatbot · Structured output with a schema · RAG chunking for a help page · Agent flow with guardrails · Cost estimate for an AI feature

Prompt and eval basics (free)