Stop by Stop

Watch real systems move data, one stop at a time.

Every topic is a metro line. Stations are the parts of a system, and the moving tag is the data riding between them. Press play and follow along. Made for interview prep, written so a first-timer can keep up.

Network map of topics

HTTP journeyREST basicsFastAPI lifecycleDjango lifecycleAuth: JWT & OAuthCelery + RedisRedis deep-diveDatabasesGit basicsPull requestsDockerDocker ComposeCI/CDNginxKubernetesAuto scalingConcurrency vs parallelismProcesses vs threadsThe Python GILMultiprocessing poolsasyncio event loopRace conditions & locksConcurrency deep-diveParallelism deep-diveThreading deep-diveMultithreading deep-diveHTTP journeyREST basicsFastAPI lifecycleDjango lifecycleAuth: JWT & OAuth4Celery + RedisRedis deep-diveDatabases3Git basicsPull requestsDockerDocker ComposeCI/CDNginxKubernetesAuto scaling1Concurrency vs parallelism2Processes vs threadsThe Python GILMultiprocessing poolsasyncio event loopRace conditions & locksConcurrency deep-diveParallelism deep-diveThreading deep-diveMultithreading deep-dive
  • Backend line
  • Async & data line
  • DevOps line
  • Git line
  • Concurrency line
  • Change lines here
  • Ride these first, in order
  • Short walk to a related stop

All lines

Backend lineAsync & data line

  1. HTTP journeyBeginnerFollow one click to a company’s computers and back.
  2. REST basicsThe slip names the parcel. The verb says what the clerk should do.
  3. FastAPI lifecycleEverything between a click and the reply.Change for the Async & data line
  4. Django lifecycleFollow a filled-in form through every checkpoint and back.
  5. Auth: JWT & OAuthThe desk keeps the passport. The valet carries only a key card.
  6. Celery + RedisBeginnerHand slow jobs to a background cook so nobody waits.
  7. Redis deep-diveA shelf in front of the storeroom, with a timer and a shout.
  8. DatabasesThe catalog finds one book, and a stack leaves together or not at all.

Git lineDevOps line

  1. Git basicsBeginnerSave points for your files, and sharing them.
  2. Pull requestsA draft stays off the book until the checks pass and an editor agrees.
  3. DockerBeginnerPack an app into a sealed kit and cook it anywhere.
  4. Docker ComposeOne plan draws a private hallway of rooms, and one door to the street.
  5. CI/CDAn assembly line that checks, boxes and ships every change.Change for the Git line
  6. NginxHands out simple mail, and shares the rest between desks.
  7. KubernetesSadia files three trays, and one window number meets the street door.
  8. Auto scalingThe rule calls two more cooks, and they cannot serve until the check.

Concurrency line

  1. Concurrency vs parallelismBeginnerJuggling many jobs, or doing them at the same moment.
  2. Processes vs threadsBeginnerSeparate kitchens, or cooks sharing one kitchen.
  3. The Python GILWhy Python cooks take turns, and when they don't.
  4. Multiprocessing poolsSend heavy work to a row of side kitchens.
  5. asyncio event loopOne cook, many dishes, a timer that says what's ready.
  6. Race conditions & locksTwo cooks, one tally, and why you need one pen.
  7. Concurrency deep-diveWho gets the one cashier next, and what a swap costs.
  8. Parallelism deep-diveTwo cashiers, one count, and the ceiling on speedup.
  9. Threading deep-diveOne cook: the contract, the counter, the door, and the pass.
  10. Multithreading deep-diveTwo cooks, one fridge, and a crew that can wait on itself.