EN

Viktor Sergeev

Senior Software Engineer · ex‑CTO & Co‑Founder

Castellón de la Plana, Spain Open to Relocation / Remote

+34 618 55 62 35

Contact me

About me

Senior Software Engineer and former startup CTO & Co-Founder with 10+ years of experience designing scalable microservice architectures and building high-load backend systems. Currently driving core platform initiatives and growth features at Semrush (an Adobe company) for 20M+ users.

Proven track record combining enterprise-grade software engineering with 0-to-1 startup leadership — from architecting complex A/B testing engines and gRPC/GraphQL services to co-founding a startup, raising $250K in Pre-Seed funding, and managing teams of up to 10 engineers.

Key expertise

Backend & Architecture
Python, FastAPI, Django, Flask, Microservices, REST, GraphQL, gRPC, PostgreSQL, MySQL, Redis, Pub/Sub, React/TypeScript (basic)
Infrastructure & DevOps
Kubernetes, Docker, Helm, GCP, AWS, CI/CD pipelines, ML model serving, LLM APIs, AI-assisted development (Claude Code, agentic workflows)
Leadership & Delivery
Technical Strategy, Team Building (0 to 10 engineers), System Design, Agile/Scrum, Project Budgeting & Cost Optimization, Investor Communication

Career

Continium ends

Semrush — an Adobe company

Senior Software Engineer

· 5 yrs 8 mos · Barcelona, Catalonia, Spain · Hybrid

Technology marketing, B2B, 20+ million users.

Key results

  • Built a personalised sign-up flow: while a user signs up, it collects data on their domain from internal teams' services, turns it into insights and shows them on the sign-up steps. In an A/B test against the old flow, sign-ups grew from 15,850 to 16,451 (+3.8%, statistically significant), trials from 709 to 745 (+5%) and first payments from 111 to 121 (+9%).
  • Co-built a self-service A/B testing platform as one of its core engineers. Before, every experiment went through an overloaded analytics team, with no history of experiments and no view of overlapping tests. Now teams run tests themselves with real-time and post-test analysis, experiment history, a view of parallel tests and warnings about sample ratio mismatch (SRM) and low test power. 20+ teams use it every month.

Responsibilities

  • Built the A/B testing service from scratch together with the team.
  • Planned the technical strategy and infrastructure development.
  • Worked with engineering heads to plan the team's part in company-wide projects with other teams.
  • Configured and maintained infrastructure on Kubernetes, Helm, Docker and GitLab CI.
  • Built a GraphQL API and integrated services over gRPC.
  • Maintained internal libraries on PyPI.
  • Ran technical interviews, onboarded and mentored new engineers.

Technologies

  • Python
  • gRPC
  • FastAPI
  • Google Cloud
  • Kubernetes
  • PostgreSQL
  • GraphQL
  • Django
  • Celery
  • pytest
  • mixer
  • Redis
  • BigQuery
  • Django ORM
  • Google Pub/Sub
  • GitLab CI
  • Helm
  • Docker
  • React
  • TypeScript
  • Webpack
  • SCSS
  • and 15 more and 17 more Show less

Continium PTE. LTD

CTO & Co-Founder

· 4 yrs 1 mo · Remote · Part-time

B2C Social Media & Creator Economy platform combining video content streaming with direct audience monetization.

Key results

  • Raised a $250K Pre-Seed investment round by designing and pitching the technical vision and product roadmap.
  • Built, hired, and managed a high-performing engineering team from 0 to 10 engineers.
  • Architected and launched 2 mobile applications from scratch on the Apple App Store and Google Play Store.
  • Successfully onboarded over 3,000 early adopters to the platform.

Responsibilities

  • Designing scalable 0-to-1 system architecture for media content delivery and monetization features.
  • Deploying and serving video classification models on Kubernetes and integrating LLM APIs into the content pipeline.
  • Leading full-cycle engineering management: hiring, interviewing, onboarding, and performance management.
  • Establishing engineering standards from scratch, including Agile/Scrum workflows, CI/CD automation, and Code Review practices.
  • Translating investor and business goals into executable technical roadmaps and product milestones.
  • Managing infrastructure budgeting, cloud service providers, third-party vendor integrations, and cost optimization.

Technologies

  • Python
  • FastAPI
  • GCP
  • Kubernetes
  • GitLab CI/CD
  • MySQL
  • Team management
  • Docker
  • CDN
  • SwiftUI
  • Kotlin
  • and 4 more and 6 more Show less

Continium starts

CS.Money

Python Developer

· 2 yrs 10 mos · Saint Petersburg · Hybrid

Finance, B2C, 10+ million transactions per day. Together with the company, we went from a startup of 10 people to a company of 200 people. I have always been a part of the core team, which implemented complex projects in a short time, for example, moving the entire infrastructure from physical servers to the cloud in 48 hours from the moment the task was set.

Key results

  • Transferred the infrastructure from physical servers in the office to the clouds.
  • Built an event-oriented architecture for conducting transactions of purchase, sale and exchange of items.
  • Fixed the calculation of user balance.
  • Moved the architecture from monolithic to microservice.
  • Set up work with large data streams in Google and Amplitude analytics and my own ClickHouse database.

Responsibilities

  • Project API support and development.
  • Integration with third-party APIs.
  • Improving code quality and getting rid of legacy.
  • DB schema design and query optimisation.

Technologies

  • Python
  • MySQL
  • Apache Kafka
  • ClickHouse
  • Flask
  • Redis
  • SQLAlchemy
  • aiohttp
  • pytest
  • factoryboy
  • DB connectors
  • RabbitMQ
  • rq
  • Bitbucket
  • Jenkins
  • Docker Compose
  • Physical VM machines
  • Grafana
  • Prometheus
  • Kibana
  • and 13 more and 15 more Show less

Mediasfera

Web Developer

· 1 yr · Saint Petersburg · On-site

Project development, B2B.

Key results

  • Increased user traffic to key customer selling pages.

Responsibilities

  • Creating and maintaining projects on the Django framework.
  • Writing animations in JavaScript.
  • Layout with templating.
  • SEO optimization.

Technologies

  • Python
  • Django
  • JavaScript
  • CSS
  • HTML
  • PHP

Education

ITMO University

Associate Degree in Software Engineering

ITMO University is specializing in Information Technology, Optical Design and Engineering.

Languages

English
B2
Russian
Native
Spanish
A1