Cheat sheets

18 one-page references, one or more for every line: the commands, formulas, templates and numbers people in each role look up. Each row links to the lesson that explains it, and every sheet prints cleanly. For single terms, see the glossary; for shortcuts and habits, see Work faster.

System Design

System design cheat sheetThe whole System Design track on a few screens: what to reach for when you see a symptom, the numbers worth remembering, the words engineers use, and what to read next. Keep it open during design reviews.For Backend Engineer, System / Solution Architect, Full-Stack Developer and more

Developer Foundations

Backend APIs cheat sheetHTTP APIs on a few screens: methods and which are safe to retry, the status codes worth knowing, headers, resource design, pagination, error bodies, auth, rate limits, idempotency keys, webhooks, versioning, NestJS and Prisma snippets, and how to test and document it all. Keep it open while you design or review an endpoint.For Backend Engineer, Full-Stack Developer, AI Engineer and moreDeveloper workflow cheat sheetThe Developer track on a few screens: the terminal commands you will type most, the Git command for what you want to do, the VS Code shortcuts worth your fingers, the JavaScript traps that catch everyone, the words engineers use, and what to read next. Each row links to the lesson that explains it. Keep it open in a tab while you work.For Career Starter, Full-Stack Developer, Vibe Coder / No-code Builder and moreFrontend React and React Native cheat sheetReact for the web and React Native on a few screens: which hook to reach for, the effect traps that cause most bugs, server data, forms, an accessibility checklist, performance fixes, Testing Library queries and the mobile specifics. Keep it open while you build or review a screen.For Full-Stack Developer, Mobile Developer (React Native), Vibe Coder / No-code Builder

Product Management

Product management cheat sheetThe Product line on a few screens: the question to ask at each stage, discovery and prioritisation tools, spec and story templates, the metrics and experiment rules, launch steps, AI product checks and how to write to stakeholders. Keep it open while you plan, write a spec or prepare a review.For Product Manager, Business Analyst, Team Lead / Engineering Manager

AI Engineering

AI engineering cheat sheetLLM apps on a few screens: a prompt skeleton, structured output, tools and MCP, retrieval (RAG), evals, agents, cost and safety, and running it all in production. Keep it open while you design or debug an AI feature.For AI Engineer, AI Builder, Vibe Coder / No-code Builder and more

Data

Data analysis cheat sheetThe analyst's toolkit on a few screens: Excel and Google Sheets formulas for what you want to do, pivot tables, cleaning steps, pandas equivalents, which chart to pick, dashboard rules and a few Power BI measures. Keep it open next to your spreadsheet or notebook.For Data Analyst, Business Analyst, Finance for Tech and moreData science and ML cheat sheetMachine learning from framing to production on a few screens: how to frame the problem, split without leaking, pick a model and a metric, forecast, explain a prediction, and keep a model healthy once it is live. Code is scikit-learn. Keep it open while you plan or review a model.For Data Scientist, AI Engineer, Data AnalystSQL and databases cheat sheetEveryday SQL in PostgreSQL on a few screens: the query for what you want, joins and window functions, indexes and query plans, safe migrations, and the commands a DBA reaches for when something is slow, locked or broken. Keep it open while you write queries or sit on call.For Data Analyst, Data Scientist, Database Administrator (DBA) and moreStatistics cheat sheetThe statistics a data analyst, data scientist or PM uses every week: describing data, confidence intervals, which test for which question, A/B test sizing, regression, and the traps that turn noise into a headline. Formulas come with Excel, Python and plain-English versions. Keep it open when you read an experiment result.For Data Analyst, Data Scientist, Product Manager

Engineering Roles

DevOps and SRE cheat sheetCI/CD and reliability on a few screens: a GitHub Actions workflow to copy, Docker, kubectl and Terraform commands, release strategies, SLO and burn-rate numbers, incident roles, a postmortem template, and the Git and Linux commands you reach for on release day and on call.For DevOps / SRE Engineer, TechOps / IT Operations Engineer, Backend Engineer and moreTechOps and IT operations cheat sheetIT operations on a few screens: Linux admin commands, systemd and journalctl, a network diagnosis ladder with Linux, macOS and Windows commands side by side, store network troubleshooting, accounts and MFA, the device fleet and the service desk. Keep it open on the support desk and on store visits.For TechOps / IT Operations Engineer, DevOps / SRE Engineer, Security Analyst (Defensive)QA and test automation cheat sheetTesting on a few screens: test design techniques, what to test at which layer, a bug report template, Playwright, Jest and Vitest commands, API and accessibility checks, fixes for flaky tests, load testing and UAT sign-off. Keep it open while you plan tests or write them.For QA Engineer, Full-Stack Developer, Mobile Developer (React Native)

Cybersecurity

Security cheat sheetDefensive security and secure coding on a few screens: the common flaws and their fixes, how to store passwords and sessions, secrets, headers, crypto choices, STRIDE, the logs worth collecting, alert triage and the first hour of an incident. Keep it open during code review, threat modelling and on-call.For Security Analyst (Defensive), Penetration Tester (Offensive), Backend Engineer and more

Architecture

Software architecture cheat sheetSoftware, solution and enterprise architecture on a few screens: quality attributes and the tactics behind them, when to pick each architecture style, who owns which data, integration patterns, an ADR template, the C4 levels, cloud cost levers, strangler-fig migration, and the enterprise basics of capability maps, value streams and the TIME portfolio model. Keep it open during design reviews and roadmap planning.For System / Solution Architect, Business / Enterprise Architect, Backend Engineer and more

Business & Finance

Business analysis cheat sheetBusiness analysis on a few screens: which elicitation technique to use when, process modelling and BPMN symbols, how to write requirements, user stories and acceptance criteria, traceability, UAT and change. Keep it open in workshops and while you write requirements.For Business Analyst, Business / Enterprise Architect, Product ManagerFinance for tech teams cheat sheetFinance for engineers, PMs and tech leads on a few screens: reading the three statements, unit economics and CAC, LTV and payback, NPV, IRR and payback with their spreadsheet functions, budgets, capex and opex, FinOps for cloud bills, and build versus buy. Keep it open when you write a business case or plan next year's budget.For Finance for Tech, Team Lead / Engineering Manager, Head of Department / CTO and more

Leadership

Engineering leadership cheat sheetLeading engineers on a few screens: what a tech lead, manager and department head each own, a 1:1 template and questions, feedback with SBI, delegation levels, the hiring loop and scorecards, performance and team health, DORA metrics, managing up, incident comms templates and cadence, design docs, slicing work, tech debt and budgets. Keep it open before a 1:1, a hiring debrief, an incident or a planning meeting.For Team Lead / Engineering Manager, Head of Department / CTO