Available for work
Tomás Guzmán
Software Engineer
I help you decide what's worth building.
About
Software Engineer with 5 years shipping full-stack web applications end-to-end. Track record building enterprise-grade real-time communication platforms, integrating payment systems, and architecting multi-tenant B2B products.
Currently Founding Engineer at a live language-learning startup.
Core stack: TypeScript, React, Next.js, NestJS, PostgreSQL, Stripe.
Experience
Founding Engineer
Talkive
- Shipped MVP to first paying customers in 3 weeks as one of two engineers, owning the platform service end-to-end (auth, Stripe billing, scheduling, admin/teacher/student portals).
- Integrated Stripe for subscription billing end-to-end (products, prices, checkout, and webhook handling), automating recurring revenue collection from day one.
- Made Stripe webhook handling idempotent: verified signatures with constructEvent and upserted payments and subscriptions on the unique Stripe invoice and subscription IDs, so retried deliveries cannot double-charge or duplicate rows.
- Cut admin list page latency from 2.3s to 230ms by collapsing a multi-join query from per-row roundtrips into a single optimized query, paired with debounced search for responsive filtering.
- Designed centralized authentication across two services: the main platform acts as identity provider, issuing JWTs consumed by a separate WebRTC classroom service. Session ownership, role checks, and user state live in a single source of truth.
- Built a timezone-aware teacher availability picker on a calendar grid with drag-and-drop, resize, and merge gestures for defining recurring weekly availability.
NestJSNext.jsTypeScriptStripeSupabasePostgreSQLOAuthMantineRender
Software Engineer
OneMeta AI
- Built and maintained a real-time audio/video and speech-translation platform deployed at Tomball ISD and integrated with leading CCaaS providers (Genesys AppFoundry ISV partner, Five9 accredited integration), routing live translation across multi-tenant contact-center deployments.
- Built server-side datagrid (filter, sort, paginate) end-to-end; collapsed three duplicated list endpoints into a single isolated service following clean-architecture patterns and cut a 13-second dashboard query to 300ms.
- Built a cross-protocol call-greeting coordination module synchronizing translated greetings across PSTN (Vonage websocket + webhook) and SIP Hairpin call legs, so both parties heard their greetings in parallel in target language followed by a start-talk beep. Pre-warmed synthesized audio in memory and cached translated text for reuse, eliminating first-greeting silence and call asymmetry.
- Led frontend architectural overhaul: established MUI design system with tokens and per-tenant theming, migrated from heavy Redux to Easy-Peasy and Zustand for clearer state ownership, and introduced a typed AxiosRepository abstraction with reusable form and side-effect hooks. Started in VerbumMeetings, consolidated in VerbumCall, replicated in Verbum Agentis.
- Built and refined the meeting-room frontend (four switchable layouts, live captions, live transcript, in-room chat) supporting up to 20 concurrent participants in real-time translated sessions.
- Wrote unit tests covering SIP Hairpin phrase-management edge cases, contributed manual test plans executed by QA, and owned the frontend for call-level logging.
NestJSReactTypeScriptMUIEasy-PeasyZustandWebRTCVonageSIP/PSTNWebSocketsMongoDB
Software Engineer
Getback
- Integrated Transbank for payment and refund flows, plus Shopify and Magento APIs to sync product and variant catalogs into the returns-selection UI.
- Stabilized a legacy React frontend by refactoring 1500-line files into 150-200 line components, tokenizing colors, and correcting state-driven UI bugs across the returns flow.
PostgreSQLExpress.jsReactReduxShopifyMagentoTransbankREST APIs
Software Engineer
KPI Managers
- Built a multi-tenant PowerBI dashboard platform for B2B clients in construction and healthcare, with subdomain-based tenant separation (e.g., clinica.kpimanagers.com), admin/user role management, and reports embedded via the official PowerBI React client.
- Refactored a legacy Express.js + Handlebars codebase into a cleanly architected Express backend with a separated React frontend, following SOLID principles.
- Implemented Redis-backed session lock to enforce single-device login per user, with 5-minute inactivity auto-logout.
MySQLExpress.jsReactReduxRedisPowerBIREST APIs
Software Engineer
CoinGroup
- Built TLM, a Binance-powered crypto trading interface: real-time price streaming, user-triggered orders, candlestick charts in Vue.js, and wallet integration.
- Authored a reusable Binance API wrapper abstracting the platform's awkward authentication and token flow, adopted by the company for downstream projects.
PostgreSQLExpress.jsVue.jsSocket.ioBinance API
Projects
Zaria AI
PrivateMulti-channel sales agent in Python (LangChain, LangGraph, LangFuse). Tool calling for inventory lookup, lead capture, payment parsing via text and image OCR, and delivery/payment routing. Deployed as a Telegram bot.
PythonLangChainLangGraphLangFuseOCRTelegram
Flowstate AI
PrivateScheduling agent in NestJS (LangChain, LangGraph, LangSmith). Captures leads, generates work quotes and estimates, and books jobs through tool calls.
NestJSLangChainLangGraphLangSmithTypeScript
Skills
Languages
TypeScriptJavaScriptPHPPythonHTMLCSS
Frontend
ReactNext.jsReduxReact RelayVue.js
Backend
NestJSExpress.jsNode.jsLaravelFlaskFastAPI
Databases
PostgreSQLMySQLMongoDBRedisSQLiteSupabaseFirebaseFirestore
Auth
OAuth
Real-Time
WebRTCWebSocketsVonage (SIP/PSTN)Socket.io
DevOps
DockerGitHub ActionsGitLinuxServer Administration
Tools
JiraLinearFigmaNotion