Zack Grooms

Backend systems engineer focused on correctness: state, invariants, transactions, idempotence.

Current focus
Building CountIQ as a systems lab: invariants → logging → Docker → AWS deployment.
Core mental model
S = Map[id → item]
S' = f(S, input)

Current state + request → new state (or unchanged state on failure).

Current Project

CountIQ — Django backend

A backend system built for predictable mutation and correctness under concurrency.

Architecture

interface → transport → service → domain → database
  • Service layer owns transactions
  • Domain layer enforces invariants
  • Idempotent endpoints
  • Retry-safe design

System Model

S = Map[id → item]
item = { id, name, qty }
S' = f(S, input)

Endpoints are state transitions. Tests prove failures don’t mutate state.

Endpoints

  • POST /items
  • DELETE /items/<uuid> (idempotent)
  • PATCH /items/<uuid>/qty (atomic delta update)

Engineering Log

Recent system work

Feb 2026 Idempotent delete

Implemented idempotent delete inside transaction.atomic(). Fixed state bug caused by filtering error.

Feb 2026 Atomic qty update

Added guarded update using qty__gte=-delta and F("qty") + delta to preserve invariants under concurrency.

About

Systems-first backend engineering

I focus on building backend systems that behave predictably: clear invariants, centralized mutation, and observable behavior.

Father of four. Engineering student. Building one system layer at a time.