Roman Sapezhko/Performance Engineer · 10+ years
I help SaaS and e-commerce teams cut latency, remove bottlenecks, and make critical flows fast and reliable.
I don’t stop at recommendations. I find what’s actually slow, prioritize by business impact, and help ship the fix.
No pitch deck. We map what’s slowing you down and what to fix first.
Try it — watch the numbers move
Production signals
beforep95 latency
820 ms
throughput
140 rps
Latency over time
~92
Lighthouse mobile
from ~38
1.7s
LCP
from ~5.4s
+35%
Throughput
B2B platform
99.9%
API uptime
under load
Fit
Self-qualify in thirty seconds. The diagnostic is free — time is reserved for teams who feel the pain in production.
How I work
Same loop whether the bottleneck is Core Web Vitals, a hot Postgres query, or a queue that melts under peak traffic.
01
Profile, traces, and production signals — not guesswork or generic audit checklists.
02
Rank fixes by conversion, reliability, and cost — so the first wins matter.
03
Implement where needed, then add monitoring, CI budgets, and delivery guardrails so it doesn’t regress.
Selected work
Some employers stay confidential — the numbers don’t.
01·E-commerce (confidential)
Slow production storefront with weak caching, manual deploys, and no performance gate. Built a foundation so releases stay fast.
02·GDS Group
Analytics took hours, throughput was capped, and deploys were slow — while holding a 99.9% API uptime bar.
03·Trust Box
Stabilized an always-on booking system after a contractor left: queues, payments, QR access, and observability.
What teams say
“Roman took our Django monolith from “works in staging” to predictable releases. API latency dropped, on-call got quieter, and we finally trust the deploy pipeline.”
“We needed real-time device telemetry without losing messages at peak load. Queues, monitoring, and clear runbooks — production stopped being a black box.”
“Clear scope, no architecture theatre. Weekly updates, tests in CI, and backend decisions explained in business terms — not slide-deck jargon.”
Sample deliverable
Example output shape — not a free full audit. Numbers illustrative of a typical SaaS checkout path.
Diagnostic summary
Acme SaaS · checkout + billing API
P0
p95 ~1.8s on pricing dependency; no edge cache; retries amplify peak latency.
Impact: Abandonment risk on mobile checkout
P1
Avg 40+ queries/request under load; missing composite index on (org_id, created_at).
Impact: Support tickets during month-end
P2
LCP regressions ship unnoticed; Lighthouse only run ad-hoc.
Impact: Slow drift after each release
Suggested next steps
Before the call, note your URL, what’s slow, and what “fixed” looks like — it makes the 30 minutes count.
The offer
You’ll leave with a clear next-step priority list — even if we don’t work together. Not a full audit. Not free implementation.
Before the call, note your URL, what’s slow, and what “fixed” looks like — it makes the 30 minutes count.
After the call
The diagnostic is free. Paid work is scoped only if there’s a fit and a measurable outcome.
Free · 30 min
Symptoms → impact → priority order. Leave with a next-step list even if we don’t continue.
Scoped after call
Deep dive on one critical path (checkout, API, dashboard) with a written findings pack and fix plan.
Scoped after call
Implement the highest-leverage fixes and add guardrails so performance doesn’t regress on the next release.
About
Performance Engineer & IT Consultant · Seville, Spain · Remote EU / worldwide · 10+ years in production
I work with teams dealing with slow applications, latency spikes, unstable performance under load, or systems that became harder to scale after rapid growth, legacy complexity, or AI-assisted development.
Background across high-load backends, IoT reliability, Core Web Vitals, CI/CD, and production troubleshooting — including OTUS Highload Architect training.
What happens next
FAQ
No. It’s a diagnostic. You’ll leave with a priority list even if we don’t work together. No pitch deck.
Not for the 30-minute diagnostic. A URL, stack notes, and what’s broken are enough. Deeper access comes later if we engage.
Django/Postgres/Redis/Celery, Next.js/Vue, nginx, Docker, CI/CD, Core Web Vitals, and production reliability practices. The method transfers across stacks.
I don’t stop at recommendations. I identify real bottlenecks, prioritize by business impact, and can support implementation.
A full audit, code fixes, or a guaranteed Lighthouse score. Those are scoped engagements after we know the problem.
If there’s a fit, we scope a focused audit sprint or a fix-and-harden engagement. If not, you still keep the priority list — no retainer pressure.
No pitch deck. We map what’s slowing you down and what to fix first.