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Capstone project for Inside the Tech Giants

Make Mangrove's Now delivery ready for the festival rush

Mangrove Market's 30-minute Now delivery takes about 60,000 app orders on a normal day and four times that at a festival peak, served by 320 stores and 600 riders. Today one NestJS API and one Postgres database run the whole path from 'Place order' to 'rider assigned'. Last festival it oversold popular items, a few riders were given two orders at once, and the order screen slowed to several seconds while a dashboard waited on six services. Ken, the engineering manager, asks you for a one-page design review that borrows at least three ideas from this course's giants at Mangrove's size, backs every choice with a load estimate, and proves the two correctness rules with working SQL: never oversell stock and never double-book a rider.

What you hand in

  1. A one-page architecture review using the template from the patterns lesson (sd-48), with a load estimate and the rung it puts the system on
  2. One diagram of the order path from the Mangrove app to the Rider app, with what moves on each arrow
  3. A Postgres schema and tested SQL for the stock reservation and the rider assignment, with the output of a run that shows a refused oversell and a refused double-booking
  4. A 'Should we copy this?' sheet for one giant's idea you decided not to adopt yet

Check your work

Tick each item when your project meets it. Be strict: this is the rubric the reviewer uses.

  • The load estimate turns orders a day into peak writes and reads per second, and names the rung
  • At least three borrowed ideas are named with the giant and the lesson they come from, each sized for Mangrove
  • Stock for every line of an order is reserved with conditional updates in one transaction, and released if payment fails
  • Rider assignment is one guarded update, so a race changes 0 rows instead of double-booking
  • Order creation and payment carry an idempotency key, so retries after a timeout are safe
  • Live rider positions and durable orders are stored differently, with the reason stated
  • The slow screen is fixed with timeouts and partial results rather than new infrastructure
  • The 'not yet' sheet names the measurement that would make you revisit the idea

0 of 8 checked

Model answer

The model answer opens once your capstone passes the review, so you can compare your work with an outline of a strong submission.

Hand in your capstone

Your links are checked automatically, then the work is scored against the rubric above, item by item, with comments. A pass counts toward the course certificate and shows on your profile.

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