eco-runtime · warm compute
low bandwidth · low impact
Brasil
build 2026.07
79KB · 6 req · 0.04g CO₂ est.
☀ thoughtful
☀ software
Matheus
Julio
Backend Engineer — Go, payments and reliable services
2+ years · acquiring · settlement · ISO 8583 · event-driven systems
system · observatory · backend metrics
static mode — connect backend for live data —
cache · hit
—
in-memory · hits / total req
░░░░░░░░░░
response · p50
—
ms · sliding 100 req
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saved · today
—
cache hits · this session
░░░░░░░░░░
co₂ · p/req
—
g · green-stack-monitor
░░░░░░░░░░
uptime · hrs
—
hours online · this session
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cat summary.txt

summary

portfolio · bash · 80×24
whoami
Backend Engineer with 2+ years of professional experience working on financial systems with Go, PostgreSQL and cloud-native tools. I have contributed to acquiring transaction authorization, settlement, clearing, reconciliation, ISO 8583 messaging and chargeback workflows. I like working with reliable services, clear rules and simple architecture; complexity should earn its place.
cat engineering.txt
A good system is usually quiet by default: clear interfaces, explicit data flow, useful tests, observable failures and deployments that are easy to repeat.
ls skills/
distributed systems payment processing PostgreSQL ISO 8583 clearing / settlement idempotency observability reconciliation cache strategies event-driven aws / cloud
ls -la work/

backend work

01
open source
payment
simulator
Distributed payment simulator in Go with RabbitMQ and PostgreSQL. It models payment processing with a double-entry ledger, resilient workers, exponential backoff and ACID transactions, focusing on consistency and operational clarity.
GoRabbitMQPostgreSQLDocker
github
02
open source
green-stack
monitor
Go middleware that estimates API carbon cost with configurable sampling, async workers, OTEL/Prometheus metrics and optional SVG badges. Built as a focused library and used by this portfolio as a small live integration.
GoOTELPrometheusopen source
github eco ping
03
professional experience
financial
flows
Worked on Go services for financial flows across acquiring and accounting domains, with focus on clearing, validation, reconciliation, settlement and traceability across the financial lifecycle.
GoPostgreSQLClearingAccounting
linkedin
04
open source
eco-runtime
portfolio
This portfolio served as a small Go backend application: in-memory cache, gzip, rate limiting, security headers, live metrics and a real integration with green-stack-monitor.
GoHTTPmetricslow cost
source
man stack

stack & notes

// backend
Go primary
Python scripts
SQL data flows
// data
PostgreSQL
RabbitMQ
MySQL
Redis
// infra
AWS
Docker
Kubernetes
// tooling
Cobra CLI
Fiber / Gorm
Migrate
// frontend
Vanilla JS
HTML / CSS
Responsive UI
// payments
ISO 8583
Clearing
Accounting
▒
dark-first design
OLED displays consume energy proportional to each pixel's brightness. a dark background literally turns those pixels off. this portfolio uses #181c18 as its base background.
dark pixels on OLED = ~0W consumption per subpixel
source: see references → OLED power
◐
desaturated colors
warm, desaturated palettes help keep average luminance low. here the aesthetic tries to serve readability and efficiency without visual excess.
warm muted has lower average luminance than neon
source: see references
⊞
cache-first backend
each avoided request means less CPU, fewer allocations and less network transfer. cache is a simple choice when data can be reused safely.
avoided req ≈ 0.0001g CO₂ not emitted (est.)
source: see references
∅
zero js framework
React, Vue and Angular require the browser to download, parse and execute hundreds of KB before rendering anything. this site uses Vanilla JS by choice: no framework, no unnecessary overhead.
bundle: 0KB framework · measured TTI < 300ms
⇲
server-side rendering
rendering on the server and serving ready HTML moves the work to optimized hardware, away from the user's device battery.
heavy work on the server · lightness on the client
↯
prefers-reduced-motion
this site respects the OS preference for reduced motion. when active, all transitions are removed: less CPU, less GPU, and a better experience for those who need it.
implemented via @media(prefers-reduced-motion)
⊕
gzip compression
gzip compresses HTML and JSON by 70-85%. implemented in the Go backend via stdlib. brotli is possible through a CDN, but depends on infrastructure configuration.
gzip at origin · brotli possible via CDN, not guaranteed
source: see references
◈
right-sized infra
single process before cluster. local cache before an external service. each layer needs to justify its own cost.
minimal infra = lower cost and lower impact
// request lifecycle
01 request reaches the Fly.io edge
02 check in-memory cache
└─ HIT → returns (~18ms)
03 MISS → Go handler runs
04 response stored in cache (TTL)
05 response compressed (gzip)
06 metrics → prometheus
07 returns to client
// choices and trade-offs
✓ Go — small runtime, low idle use
✓ in-memory cache — no Redis required
✓ gzip via Go stdlib
✓ token bucket rate limiter
✓ vanilla JS — zero app framework
✗ no heavy ORM
✗ no Kubernetes for a personal site
// carbon awareness
the backend can call electricitymap.org to expose current carbon intensity for the BR-CS grid.
values are cached for 1 hour because grid carbon intensity does not need per-request refreshes.
exposed through /api/metrics → carbon_intensity_gco2kwh
HTTPArchive · Web Almanac 2024
baseline for page weight and request count. 2024 desktop median: ~2.6MB and ~67 requests per page.
almanac.httparchive.org/en/2024 ↗
websitecarbon.com · calculation methodology
model used to estimate CO2 per visit from data transfer, carbon intensity and device mix. the 0.04g value is derived from this model and page weight.
websitecarbon.com/how-does-it-work ↗
sustainablewebdesign.org · Sustainable Web Design Model
reference model for estimating emissions from digital systems, including cache-related savings.
sustainablewebdesign.org ↗
Google · OLED display power consumption study (2021)
Android team study showing that dark OLED pixels consume near-zero watts. dark mode reduced battery use by 14-60%, depending on brightness.
dl.acm.org · OLED energy study ↗
web.dev · Brotli compression
brotli is typically 15-25% smaller than gzip for HTML, CSS and JS, with broad modern browser support.
web.dev/codelab-text-compression-brotli ↗
note on estimates: values marked with "est." are derived, not directly measured. CO2 per cache hit, energy savings and market comparisons are approximations based on the methodologies above. they are scale references, not an audit.
./eco-report --full

eco report

page weight
79
KB total
lean
js bundle
0
KB framework
zero
co₂ / visit
0.04
grams · est.
low
http requests
6
total
lean
time to interact
<0.3
seconds
fast
power draw
LOW
estimated
eco
this portfolio vs market median [1]
total transferred2.6MB → 79KB[1]
http requests~67 req → 6 req[1]
javascript bundle~500KB → 0KB
co₂ per visit est.~0.5g → 0.04g[2]
annual energy est.~0.4 kWh/year[3]
efficiency per layer
cache hit rate—
░░░░░░░░░░
gzip compression (config)~80%[5]
░░░░░░░░░░
cdn offloadnot configured
notes: "market standard" values are medians from the HTTPArchive Web Almanac 2024. CO₂ calculated via Sustainable Web Design Model. estimates marked as "est." — see full references.
requests avoided by cache
0
total this session
how I like to work
01cache before computing
02fewer requests, more efficiency
03observe before optimizing
04less abstraction, when possible
05lean infra is sustainable infra
06low brightness is a technical choice too
07keep it simple until complexity earns its place
./contact --init

contact

available channels ● online
--emailmatheusjsant@gmail.com→ --githubgithub.com/MatheusJulioSantana→ --linkedinlinkedin.com/in/matheusjuliosantana→ --eco-pingcurl /eco→
root@eco:~$