Ahmad Hamza

Guest storefront and catalog policy engine

stack: rails 8 · graphql · open search

Built a complete unauthenticated storefront (product discovery, guest checkout, organization branding) and an enterprise catalog-restriction system giving stores control over which products and brands their patients can see: new data model, restriction services, a GraphQL batch mutation, and enforcement across segmentation, favorites, spotlight, and checkout subtotals.

Wired the restrictions into OpenSearch as well: a clause generator that injects exclusion filters into all typeahead query builders and both GraphQL search services, plus index mapping and serializer changes shipped through a multi-stage reindex workflow. Kept enforcement fast with cached restricted-id lookups invalidated on commit.

Rebuilding the disapproved-ads pipeline for 300 merchant accounts

stack: rails 7 · sidekiq · google apis · new relic

Desertcart manages roughly 300 Google Merchant Center accounts, each holding between 150 thousand and 15 million products. The legacy system for handling disapproved ads scanned everything and took days to run. I redesigned it around the Reporting API to fetch only disapproved products, built a parser with modular handlers for price mismatches, availability errors, and blacklisted items, and restructured the work into batch-based jobs that survive deployments mid-run.

I also built a Slack alerting system and New Relic dashboards that flag disapproval and expiration issues before account-suspension thresholds are breached.

CPU usage cut by more than 70 percent. Runtime went from days to hours.

Platform engineering on Toptal's Core Team

stack: rails 7 · nodejs · bigquery · graphql · custom generators · slack bots

Engineering insights platform. Worked on the platform that surfaces contribution metrics across GitHub, Jira, and internal review systems for 500+ engineers, enabling data-driven decision-making at Toptal. For the module I built, I introduced a convention-driven approach for defining new metrics and a custom Rails generator that scaffolds the boilerplate, so adding a metric became a routine task instead of a design discussion. I wrote about that module's design in Scaling Through Convention.

Screening operations. Led two initiatives on Toptal's high-volume screening platform: simplified technical assignment submissions so candidates submit directly through the portal (less friction for talents, hassle-free for screeners), and revamped screening steps to eliminate repetitive processes and improve efficiency.

Incident and review tooling. Contributed to incident management tooling and its Slack bots on Node.js (call escalation flows during incidents, status-change validation for notifications, Jira integrations), alongside the peer review and appraisal system.

Payments and compliance for a regulated gaming platform

stack: rails 6 · react js · postgresql · 30+ payment gateways

Built and maintained an online casino platform where players manage balances, deposits, and withdrawals across more than 30 payment gateways. Developed the anti-addiction mechanism (deposit limits and self-exclusion) that kept the platform compliant with regulatory standards for a base of over 1 million players, and shipped a lottery system that measurably lifted player engagement.

JustInvoicIt

stack: rails 8 · hotwire · turbo · stimulus · bootstrap

A monolithic Rails 8 SaaS that helps freelancers create invoices and send payment requests fast. It doubles as my proving ground for modern Rails frontend work with Hotwire, Turbo, and Stimulus, and as a mentoring vehicle: I have interviewed and trained junior engineers here, screening for aptitude over memorized syntax. The one I am proudest of: teaching a practicing doctor to program, from zero to contributing working code. Happy to walk through a live demo.

Client delivery on legacy systems, ad tech, and media

stack: rails · javascript · google apis

Four and a half years of client work, promoted twice from Software Engineer to System Analyst. Led a team of six engineers on a legacy project, handling multiple deliveries, refactoring, and performance improvements while keeping the client's release schedule intact.

Built the feature that let a digital marketing agency run occasion-based targeted Google Ads campaigns, which boosted the client's business. Also developed and maintained a media transcription platform where freelancers log transcriptions across video, image, and document types, manage task assignments, and receive payments.