Software Engineer

Company Description

Upsell.com empowers Shopify and Wix merchants to unlock additional revenue from every order through optimized upselling and cross-selling opportunities. Our app enables seamless upsell and cross-sell integration across touchpoints, including product pages, carts, checkouts, and thank-you pages. Trusted by over 40,000 ecommerce brands and rated 4.8/5 by thousands of Shopify users, we offer a simple, effective, and quick-to-set-up solution. By personalizing recommendations and strategically placing offers, we help businesses increase average order value while maintaining an excellent customer experience.

Responsibilities

• Design, develop, and maintain scalable backend systems using Node.js (JavaScript / TypeScript)
• Participate in system architecture decisions, including service boundaries, data flow, and scalability strategies
• Analyze and optimize performance, memory usage, and resource consumption
• Build and maintain services that operate reliably under high load and real production traffic
• Identify bottlenecks, failure points, and scalability limits before they become production incidents
• Use AI-assisted development tools effectively while understanding their limitations
• Collaborate with other engineers and (optionally) lead technical execution within the team

Skills & Experience

General Experience

• Minimum 3 years of professional experience in software development
• Experience working on production systems with real users and traffic

Computer Science & Web Fundamentals

Strong foundation in computer science basics, including:

• How internet applications work end-to-end
• Network layers and common protocols (HTTP, TCP/IP, etc.)

Understanding of:

• Network latency and packet loss
• Timeouts, retries, and backoff strategies
• Typical communication errors and failure scenarios

Ability to analyze and optimize server resource usage:

• CPU
• Memory
• Disk I/O
• Network

Node.js & JavaScript Ecosystem

• Strong hands-on experience with Node.js for backend development
• Solid knowledge of JavaScript and TypeScript, both backend and frontend
• Deep understanding of how Node.js works internally, including:
• Event loop and asynchronous execution model
• Memory management and garbage collection
• CPU-bound vs I/O-bound workloads
• Awareness of Node.js weak points (e.g., blocking operations, memory leaks, GC pauses)
• Proven ability to apply mitigation and optimization strategies

Databases & Data Modeling

Practical experience with:

• MySQL (schema design, indexes, transactions, performance tuning)
• MongoDB (document modeling, indexing, consistency trade-offs)
• Understanding of relational vs NoSQL data models
• ClickHouse experience is a plus (analytical workloads, aggregations, performance)

Microservice Architecture

Strong understanding of microservice architecture principles, including:

• Service boundaries and ownership
• Inter-service communication
• Data consistency and eventual consistency
• Trade-offs vs monolithic architectures

Experience dealing with real microservice challenges:

• Latency
• Partial failures
• Versioning and backward compatibility

AI-Assisted Development

• Understanding of how AI code generation works at a high level
• Awareness of the strengths and limitations of AI-generated code

Ability to:

• Use AI tools to increase development speed and productivity
• Detect incorrect, unsafe, or inefficient AI-generated solutions
• Mitigate risks such as hallucinations, over-generalization, and hidden bugs
• Treat AI as a tool, not a replacement for engineering judgment

High-Load Systems & Performance

Clear understanding of the difference between:

• “It works on my computer.”
• “It works under real production load.”

Experience with:

• Load-related failures
• Bottlenecks that only appear under concurrency

Knowledge of high-load optimization techniques, such as:

• Caching strategies
• Concurrency control
• Asynchronous processing
• Backpressure handling
• Ability to reason about scalability limits and plan ahead

Good to have, will be an advantage

Compiled Languages

Experience with compiled languages, such as:

• Rust
• Go
• Understanding of performance characteristics, memory safety, and concurrency models in compiled runtimes

Leadership & Management

Experience or interest in technical leadership

Ability to:

• Break down complex problems into executable tasks
• Distribute work within a team
• Track progress and ensure timely delivery
• Strong communication skills and an ownership mindset

What We Value

• Deep technical understanding over surface-level knowledge
• Ability to explain why a solution works, not just how
• Pragmatic engineering decisions based on real constraints
• Curiosity, responsibility, and long-term thinking