Senior backend developer · Taubaté, Brazil

Gustavo Eklund

I develop payment systems, mostly with Pix.

History gustavo@eklund.com.br ⌘K navigate
— KB over the wire0 dependencies
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— fpsmeasured now, in your browser
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    02 Profile

    Seven years building software, five of them in payments. More than 10 years in IT overall.

    I'm a senior backend developer. I've worked at a digital bank, at a credit platform for banking correspondents and, since 2024, at OKTO Payments, a multinational payments company.

    At OKTO, the Brazil payments team rebuilt the company's Pix. OKTO is a direct participant in the SPI, the Central Bank system that settles Pix payments. We delivered sending and receiving Pix, key lookups, QR Code, Pix Automático and biometric Pix through Open Finance, all approved by the Central Bank.

    Before that, I led two teams, one of 4 people and one of 5. Each delivered a complete platform, from architecture and back end to apps, infrastructure and deployment.

    Day to day I write Go and TypeScript. I use DDD, Clean Architecture, CQRS and Event Sourcing to model systems, and Grafana, Loki, Prometheus and k6 to monitor and test them. I also develop with coding agents, such as Claude Code, Codex and Cursor, and write the specifications they follow.

    Observability · OKTO Payments · Pixnumbers from my résumé, illustrative curveslast 24 h
    Transactions / day
    2 million+
    Peak
    ~500TPS
    p95 latency
    200ms
    p99 latency
    300ms
    Availability
    99.9%
    Countries
    7
    Throughputtransactions per second · Pix
    Latencyms · critical Pix servicesp95p99reference 300 ms
    Availabilitylast 30 days · 99.9% · one partial degradation
    View as a table (hourly)
    HourAvg TPSMax TPSp95 (ms)p99 (ms)

    03 Architecture

    Architecture of a Pix, from the app to the Central Bank.

    This map is a simplified version of how a payments company connected directly to the SPI processes a Pix. I built it from the Central Bank's Direct Participation Roadmap, Timing Manual and Pix Security Manual. The traffic is simulated. Hover a service to see what it does, or click follow a Pix to watch one payment from start to finish.

    simulated trafficload —TPS —replicas —
    View as a list of services

    04 Load test

    I wrote a load test that runs in your browser.

    The test fires payments at a simplified Pix engine that I also wrote. Both run in the background of your browser, using Web Workers, and the output imitates k6, a load-testing tool. The engine validates each payment, rejects duplicates, tracks the balance of 10 thousand accounts and records everything in a hash-chained journal. The numbers are measured on your computer, on this visit.

    k6-ishscenario ramp · — workers · stages 5s ↑ · 10s = · 5s ↓waiting
    ThroughputPix per second · dashed line = ramp stage
    Latency per batchms per batch of 1,000 Pix · rolling p95 and p99p95p99
    Distributionbatches per latency bucket
    Pix processed
    —
    Peak
    —/s
    p95 per batch
    —ms
    p99 per batch
    —ms
    Per Pix
    —µs
    Duplicates blocked
    —
    Insufficient funds
    —
    Checks
    —/5

    05 History

    Where I've worked.

    Four companies in seven years. The cards advance on their own, or click one to open it.

    OKTO Payments is a payments company operating in 7 countries and processing more than €17 billion a year. We rebuilt its Pix infrastructure so the company could be a direct participant in the SPI. Today that means more than 2 million transactions a day, with peaks of about 500 per second and 95% of responses within 200 ms.

    We went through the Central Bank certifications for receiving Pix, sending Pix, QR Code, key lookups on the DICT (with a token bucket), Recurring Scheduled Pix and Pix Automático. We also delivered biometric Pix through Open Finance (JSR) with ITP, and boletos through BaaS. We use Grafana, Loki and Prometheus dashboards to track success rate per client and latency percentiles, and we test load with k6.

    • Go
    • TypeScript
    • SPI
    • DICT
    • Open Finance
    • Grafana
    • k6
    Certification completedCentral Bank · Pix Automático
    p99 · 300 ms99.9% availability

    An online credit system (multi-tenant SaaS) for banking correspondents, with thousands of customers. Each correspondent configures and runs its own loan portfolio, and the commission is calculated on the profit of each operation.

    I led a team of 4, from the multi-tenant architecture to the commission engine. I also handled the deployment and all the infrastructure on my own, on VPS.

    • Multi-tenant
    • Commissions
    • VPS
    • Deploy
    Team of 4tech lead, end to end
    Infra on VPSself-managed deploys

    A white-label digital bank, for Android and iOS, built for an institution that takes part in Pix through another bank (an indirect participant). It had accounts, statements, onboarding with KYC and KYB, TED and DOC transfers, boletos, investments and full Pix: receiving, sending by key, QR Code or bank details, and managing keys and portability.

    I led a team of 5 that delivered the whole platform in a few months, with infrastructure on Google Cloud, CI/CD and publishing on the App Store and Google Play.

    • Clean Architecture
    • DDD
    • CQRS
    • Event Sourcing
    • Google Cloud
    • CI/CD
    Apps publishedApp Store · Google Play
    Full PixDICT · key portability

    An internal web management system for a higher-education institution, with REST APIs, automated tests, CI/CD and automation libraries. It ran on physical Linux servers that I installed myself.

    I also did structured cabling, rack and switch setup, mass cloning of workstations and operations support.

    • REST
    • CI/CD
    • Linux
    • Networking
    Servers upphysical Linux · cron · local git
    Green CIautomated tests

    Education · Fatec Taubaté, Systems Analysis and Development (2023) · Etec Pindamonhangaba, IT Technician (2018)

    Courses · Clean Code and Clean Architecture, Rodrigo Branas (2022) · Advanced Node.js with TDD and Clean Architecture, Rodrigo Manguinho (2021)

    06 Contact

    Let's talk.

    Send me an email. Click the address to copy it.

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