Senior Full-Stack Engineer (Contract) — Inventory & FBA Replenishment Platform

About us

We run a multi-channel e-commerce business with our own warehouse plus Amazon FBA. We’re building an internal web app to manage inventory, plan reorders, and generate compliant FBA shipments. This is not a generic “shop dashboard.” We need something that actually reflects how stock moves in the real world (batch-based, FIFO, GST/HSN, etc.).

What we’re building (the app needs to do this)

• Track stock by SKU and Batch. Each batch is separate and FIFO rules apply — no mixing.

• Plan supplier reorders using ADU (avg daily units), seasonality, and 3 manual “on order” buckets.

• Plan FBA replenishment based on target days of coverage, with warnings if FBA stock is getting risky.

• Flag Excess Inventory.

• Export FBA allocation with all compliance fields per batch.

Scope / core modules

1. Inventory Engine

• Immutable ledger of all movements.

• Per-batch balances.

• No negative stock allowed (must fail atomically if an allocation tries to overdraft).

• “Compliance pending” batches that exist in the system but cannot be shipped until paperwork is done.

2. Replenishment Planner

• Reorder targets driven by ADU rules:

• If ADU > 6 → target 4 months of stock

• Else → target 3 months

• Seasonality uplift and preseason warnings.

• 3 manual ordered buckets (ordered_1 / ordered_2 / ordered_3).

• Flags:

• “Less than Sellerboard” (we’re below their suggested stock)

• “Low FBA” (FBA at risk).

3. FBA Shipment Planning

• Import an FBA plan (SKU, Qty, FC code).

• Allocate that demand FIFO from existing batches.

• Export (per split) with these columns:

• Batch ID

• SKU

• Amazon STN Price

• GST Rate

• HSN Code

• Product Name

• Quantity

• FC Code

4. Imports / Data Feeds

We’ll pull from:

• Sellerboard: Estimated Sales Velocity, FBA/FBM stock, Reserved.

• Receiving: batch compliance info incl. base_cost (INR / RMB / USD).

• Manual POs / orders: ordered_1 / ordered_2 / ordered_3.

• Seasonality profile per SKU.

5. UI (can be simple but must be usable)

• Planner tabs: “Order from Supplier” / “Send to FBA.”

• Batches & compliance queue.

• Excess stock view.

• Seasonality view.

• Users & Access / basic roles.

What you will own

You will recommend and build the first working version end-to-end.

That includes: data model, backend, frontend, API layer, auth, deployment.

We are not married to any stack. You tell us what’s fastest, reliable, and maintainable.

What we need from you (must-have)

• You’ve shipped production software that touches inventory, warehouse ops, supply chain OR e-commerce analytics (FBA experience is a big plus).

• You’re comfortable making DB design decisions (ledger, batch tables, constraints, etc.).

• You write clean code with tests and are okay demoing progress every week (IST-friendly hours).

• You work directly in our repo.

How we’ll work

• Milestones with weekly demos.

• Code lives in our Git repo.

• Tests are required (no “it works on my machine”).

• Start ASAP (must be comfortable collaborating in IST time zone).

How to apply (please include all of these)

1. Links to 2–3 relevant repos or demos (can be private screenshots if code is private, that’s fine).

2. In 3–5 lines: how you would prevent negative stock at the database level so that two parallel allocations can’t oversell the same batch.

3. A short outline (SQL or logic) for FIFO batch allocation when creating an FBA shipment.