Problems

Each problem is a small multi-file project with seeded bugs (or a missing feature), visible tests and hidden tests. Pick one, fix it, and submit. Problems marked Sign in need a free account.

• 21

  21Gift Card Wallet API

  Gift card wallet REST API (codes, ownership, expiry, idempotent redemptions)

  Java · Spring BootEasyBug fix60 min
• 22

  22Dock Appointment Booking API

  Dock appointment booking REST API (door choice, half-open slots, validation)

  Java · Spring BootEasyBug fix60 min
• 23

  23Price Drop Alert API

  Price-drop alert REST API (alert limits, CSV price feed, triggers)

  Java · Spring BootEasyBug fix60 min
• 24

  24Review Helpfulness Votes API

  Review helpfulness votes REST API (implement rank; votes, burying, tie-breaks)

  Java · Spring BootEasyFeature60 min
• 25

  25Return Authorization API

  Return authorization (RMA) REST API (policy windows, restocking fees, lifecycle, ownership)

  Java · Spring BootMediumBug fix60 min

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• 26

  26Shipment Tracking Events API

  Shipment tracking events REST API (pipe feed, duplicates, out-of-order scans, late flag)

  Java · Spring BootMediumBug fix60 min

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• 27

  27Loyalty Points Ledger API

  Loyalty points ledger REST API (implement plan; expiring lots, FIFO redemptions, retries)

  Java · Spring BootMediumFeature60 min

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• 28

  28Warehouse Pick-Wave API

  Warehouse pick-wave REST API (wave packing, serpentine walk, pick-list totals)

  Java · Spring BootMediumBug fix60 min

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• 29

  29Multi-Warehouse Order Allocation API

  Multi-warehouse order allocation REST API (single-vs-split, reservations, retries, ties)

  Java · Spring BootHardBug fix60 min

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• 30

  30Refund Processing API

  Refund processing REST API (implement split; idempotency order, money parsing, window, reasons)

  Java · Spring BootHardFeature60 min

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