Build it, break it, see the result

Build a short-link service from parts, press Run, and see whether it shortens, redirects and counts clicks, and whether it keeps doing so when a server, the cache or the click worker dies.

Build a home-feed service from parts, press Run, and see whether it saves posts, opens feeds and delivers every new post to the followers, and whether it keeps doing so when a server, the feed cache or the fan-out worker dies.

Build the back end of a chat app from parts, press Run, and see whether it stores messages, shows who is online and sends an alert to a closed app, and whether it keeps doing so when a connection server, the cache or the alert worker dies.

Build a marketplace search box from parts, press Run, and see whether it returns products, serves suggestions and gets a seller's change into the index, and whether it keeps doing so when an app server, a search node or the indexing worker dies.

Build Safar's ride service from parts, press Run, and see whether it stores where drivers are, finds the ones near a rider, saves trips, and keeps going when an app server, a node of the location map or the trip worker dies.

Build the system behind a ticket drop from parts, press Run, and see whether it can hold seats, show which seats are free and confirm payments when 8,000 requests a second hit it at ten o'clock, and whether it keeps going when an app server, the seat-map cache or the payment worker dies.

Build DalilBot from parts, press Run, and see whether it fetches pages, saves them and sends the links it finds back as new work, and whether it keeps going when a fetcher, the seen-URL memory or the page parsers stop.

Build a video platform from parts, press Run, and see whether videos play and uploads become playable, and whether the service keeps going when a CDN network, an app server or the transcoding workers stop.

Size an AWS web tier for launch day, then survive losing a zone.

Route traffic through an Ingress and a Service to a Deployment, and let the HPA size it.

Run a proxy, app containers and Postgres, and find which container limit bites first.

Put nginx, an app service and PostgreSQL on hosts and see which one runs out of cores.

Push load into one app tier and watch p99 climb once it passes the knee.

Size Daftar's load balancer (the front door that spreads traffic), app machines and database for exam week, then make it survive losing a zone (one data centre).

Put a cache in front of Wasla's links store so 100,000 redirects a second never reach the database.

Run real commands on any device, then step through the packet they sent, one hop at a time.

Two office PCs cannot reach the server two routers away. Find the three faults with real commands and fix them.

The school has one block, 10.20.0.0/22. Give every group its own block that fits its devices, with no overlaps.

A laptop and a server sit on different subnets. Place them, add a router, cable everything and set the addresses until they can talk.

A home router shares one public address with every device behind it. Make the laptop reach the outside server, let the outside server reach the home web page through a forwarded port, and keep the guest network away from the home devices.

A laptop is plugged into the home network and cannot load a page. Walk up the layers from the cable to the web page, find the three faults, and fix each one where it lives.