Олександр

Oleksandr Bunin
Senior Fullstack Engineer
[open contact info](look above in the "contact info" section) | [open contact info](look above in the "contact info" section) | Kyiv | [open contact info](look above in the "contact info" section)

Summary
Senior Full-Stack Engineer with 8+ years building production-grade, high-concurrency SaaS, specializing in React,
Java with Spring Boot, and Python with FastAPI, backed by PostgreSQL and Redis, deployed on AWS and SAP
BTP Cloud Foundry with Docker, Kubernetes, and CI/CD pipelines. Built an AI workspace orchestrating 40+
LLM, image, and video models with LangChain and LangGraph multi-step agent workflows over RESTful APIs
and SSE streaming, and architected enterprise platforms serving 500+ tenants and tens of thousands of users. Strong
in low-latency service design, event-driven architecture, and reusable component systems, having led a legacy to
microservices to Spring Modulith evolution, used Protobuf for compact serialization, and run an observability and
resiliency program that cut MTTR roughly 60%. Comfortable owning architecture end to end, defining engineering
standards, and shipping the full path from data model to frontend experience.

Technical Skills
Backend & Languages: Golang, Java, Spring Boot, Spring Modulith, Spring Security, Python, FastAPI, Node.js,
Hibernate, gRPC, REST
AI & Agentic: LangChain, LangGraph, Multi-Agent Orchestration, Tool Execution, LLM Orchestration, SSE
Streaming, Prompt Engineering, Context Engineering, RAG
Frontend: React, Next.js, TypeScript, TanStack Query, Zustand, Redux Toolkit, Tailwind CSS, shadcn/ui, Radix UI,
MUI, Reusable Component Libraries
Cloud & DevOps: AWS, SAP BTP, Cloud Foundry, Docker, Kubernetes, Helm, Terraform, CI/CD Pipelines,
GitHub Actions, Jenkins, Cloudflare
Data & Messaging: PostgreSQL, SAP HANA Cloud, MongoDB, MySQL, Redis, Kafka, RabbitMQ, SAP Event
Mesh, Protocol Buffers
Architecture: Microservices, Spring Modulith, DDD, Event-Driven Systems, Strangler Fig, SAGA, CQRS, Multi-
Tenant SaaS, Resilience4j
API & Protocols: REST, gRPC, WebSockets, Server-Sent Events, OAuth2, OIDC, JWT, mTLS

Professional Experience
06/2024 – Present Senior Full-Stack Engineer
Remote LeverX International LLC
High-performance internal SaaS used daily by SAP Account Executive teams worldwide to
model enterprise deals across TCV, ACV, LEP, and IT1 and IT2 calculations over multi-
year, multi-product scenarios.
Led the platform's evolution from a legacy monolith to microservices to Spring
•

Modulith, using the Strangler Fig pattern to migrate incrementally and cutting p95
latency by replacing HTTP and Event Mesh calls with in-process events.
Designed an immutable snapshot store for every deal change, serialized with Protocol
•

Buffers and made storage-efficient through structural sharing, paired with a domain
event log for audit and analytics.
Built real-time multi-user collaboration over WebSockets with SAP Event Mesh and
•

optimistic concurrency control, surfacing edit conflicts to clients to prevent lost updates.
Added resiliency with Resilience4j, using Circuit Breakers and idempotent Retry with
•

backoff to stop cascading failures when upstream SAP systems degraded.
Provisioned infrastructure as code with Terraform on SAP BTP Cloud Foundry,
•

with typed variables, remote state, and terraform plan posted to PRs for reviewed infra
changes.
Cut MTTR by roughly 60% over a year through Jaeger tracing, structured ELK
•

logging, and customer-impact-tuned alerting.
Led the React and TypeScript UI, building a reusable component system with
•

optimistic updates and rendering tuned for multi-thousand-line deals.
Enforced DDD aggregates and domain invariants, with architecture tests guarding
•

module boundaries at compile and test time.

Migrated the platform from Java 11 to Java 25, adopting modern language features and
•

bringing dependencies current to improve performance and maintainability
Redis for caching of frequently accessed deal and pricing data, reducing repeated
•

database reads and keeping scenario calculations fast under load.

03/2024 – 06/2024 Senior Software Engineer, 3-Month Contract
Remote Promtheon
AI SaaS platform aggregating 40+ LLM, image, and video models into a single agentic
workspace.
Led development of the Golang orchestration layer that routes requests across 40+
•

LLM, image, and video providers behind a unified API, normalizing divergent auth,
rate-limit, and payload schemas so new models onboard via config alone, and isolating
per-provider failures so one degraded upstream cannot stall unrelated agent runs.
Built multi-step AI agent workflows with LangGraph for autonomous reasoning and
•

tool execution, managing context windows, tool-call routing, and intermediate state to
keep long agentic loops coherent and cost-controlled at scale.
Engineered low-latency SSE streaming for real-time agent responses, handling
•

backpressure, partial-token flushing, and mid-stream cancellation to keep time-to-first-
token low even under concurrent sessions.
Led the backend data layer and APIs in Go and Python with FastAPI for chat,
•

document processing, and agent tooling, with Redis-backed caching and dedup keys
that cut redundant model calls and controlled cost under repeated context.
Drove the end-to-end delivery across architecture, development, deployment, and
•

operations on AWS with EC2, RDS PostgreSQL, S3, CloudFront, and Route 53,
defining the service patterns, conventions, and observability for the platform.
Hardened delivery behind Cloudflare with Docker-based deploys, managing DNS, edge
•

caching, and TLS to keep the multi-model gateway resilient under variable, bursty load.

04/2018 – 03/2024 Senior Backend Engineer
Remote LeverX International LLC
Multi-tenant SaaS on AWS dispatching work to tens of thousands of field technicians
across 500+ customer tenants.
Improved the dynamic plugin compilation pipeline, cutting compilation latency by
•

roughly 90% through response compression and caching of compiled artifacts, removing
a recurring source of slow plugin loads under multi-tenant load.
Developed features across a 20+ microservice ecosystem on Java and Spring Boot plus
•

selected Node.js integration services, while maintaining strict multi-tenant domain logic
and tenant isolation across the platform.
Built Kafka-based event flows using the Transactional Outbox pattern to guarantee
•

database and event consistency, eliminating dual-write inconsistencies that previously
caused divergent state between services in the dispatching pipeline.
Integrated distributed tracing with Jaeger across the 20+ services, turning cross-service
•

debugging from hours of manual log-grepping into minutes and enabling data-driven
decisions on where latency bottlenecks lived.
Optimized PostgreSQL performance under production load by restructuring queries
•

and indexing to reduce query execution time and raise system throughput during peak
dispatching volume.
Maintained shared platform libraries for tenant context, structured logging, trace
•

propagation, metrics, and auth, standardizing observability and security across the entire
microservice fleet.
Wrote and maintained backend unit and integration tests plus Python E2E suites across
•

multiple microservices, sustaining roughly 90% coverage with reliable E2E runs gating
production deployments, supported Kubernetes and Helm deployments, and enforced
SOLID principles and modular architecture to sustain long-term maintainability.

Education
09/2024 – 02/2026 Master's Degree, Computer Software Engineering
Open International University of Human Development "Ukraine"
09/2016 – 06/2020 Bachelor of Science in Applied Mathematics
Kyiv Polytechnic Institute, Physical-Technical Institute