Tsailing Fung (Lillian)

Senior Software Engineer — Backend / Fullstack
Senior Backend Engineer with 8+ years of experience building scalable distributed systems in payroll, staff management, and financial reporting / notification platforms. Expertise in designing secure service-to-service integrations, high-availability architectures, and event-driven financial workflows. Proven ability to modernize legacy systems, improve reliability, reduce operational overhead, and deliver production-ready systems.
Languages
Python, Ruby, Java, Kotlin, SQL, TypeScript, Go
Distributed Systems & APIs
gRPC/Protobuf, REST, Kafka, SQS, Lambda
Cloud & Infrastructure
AWS, Kubernetes, Terraform, Docker
Data & Observability
MCPs, Snowflake, Datadog, Looker
Block
Senior Software Engineer – Backend
10/2021 – Present

Software Engineer – Fullstack / Backend
07/2019 – 10/2021

(formerly Square)
  • Reliability & production scale — Operated and enhanced 15+ mission-critical payroll and staff management services serving 4M+ Square merchants, consistently meeting P99.99 availability SLOs and maintaining 500ms P99 latency in production.
  • Core product system ownership — Led delivery of high-priority features for the Tip Attribution Service, improving customized tip distribution for 90% of merchants, and contributed to 15+ production services across time tracking, scheduling, and compliance enhancements.
  • API & system integrations — Designed and implemented cross-system integrations: co-led beta launch of Team APIs job management endpoints for third-party developers, built secure RPC integrations between Cash App Taxes and Payroll to automate W-2 imports, and developed a tax filing transmitter covering all 50 states using event-driven workflows (SQS + Lambda).
  • Infrastructure & cost reduction — Reduced Payroll database size by 30% and lowered operational overhead by architecting a DynamoDB-based archival system; introduced Terraform-based infrastructure provisioning for improved scalability.
  • Initiative & AI innovation — Built an automated file conversion pipeline (90% success rate) and introduced an internal chatbot integrated with team support channels, standardizing documentation across 90% of recurring support cases and driving cross-team adoption.
Carta
Software Engineer – Fullstack
09/2016 – 05/2019

(formerly eShares)
  • Technical ownership — Designed and owned development of a next-generation Financial Reporting platform, automating equity valuation and scalable data generation by decoupling calculation and reporting pipelines; implemented financial models (DCF, comparables) to support analyst workflows.
  • Core platform development — Refactored legacy task processing systems to improve throughput and reliability, built RPC services for trading data ingestion, and developed internal CRM tooling to automate contract management and sales pipeline visibility.
UC Davis / Exploratorium
Research Assistant
09/2013 – 06/2016
  • Research analysis — Built Django-based backend services and interactive visualizations, integrating five heterogeneous datasets for academic research and public exhibits to surface patterns and insights.
Football Squares Trip Vis