Engineering

Fidelity under hard constraints.

Eric Xi Xin Liang is a principal-level architect of distributed systems: cloud infrastructure, permission modelling, real-time pipelines and AI platforms. He is also building a product of his own, and brings a founder's eye for users, cost and market to the companies he works for.

GitHub · ExxLiang193 (opens in a new tab)

Method

Find the root cause instead of iterating on symptoms. Treat the constraint as the design brief. Generalise from fast feedback loops, and write the decision down.

That now includes working with AI coding agents: spec-first delegation, review tiered by risk, and standards written so an agent can apply them and be checked against them.

The same habit drives the piano reductions: an orchestral score compressed into ten fingers with as little loss as possible.

Product sense

The user's experience, the unit cost and the market are part of the engineering problem. Founder habits, applied inside a company as much as in his own.

  • Interaction design

    A canvas application with its own camera system, SVG annotation primitives and keyboard-driven workflows, held to one identity and interaction philosophy as it grew. Platform-coherent interfaces over generic patterns.

    Where: FounderOptikka

  • Unit economics

    Cost designed in rather than audited afterwards: image processing and AI queries at fractions of a cent each, infrastructure cost cut by about 40% while usage tripled, and per-service cost models across three growth scenarios with gross-margin projections.

    Where: FounderOptikkaRedflag AI

  • Shipping to a customer

    An AI platform delivered to a major broadcaster within four months of joining, which became the company's flagship enterprise relationship. A natural-language audit-log search shipped in a week and a half.

    Where: Optikka

  • Go-to-market

    Competitive positioning, content-platform economics and retention incentives for instructors and students. A seat in top-level negotiations with CDN partners and enterprise clients.

    Where: FounderRedflag AI

Selected work

Problem, constraint, approach, result. Client names and figures are kept general.

ProjectProblemConstraintApproachResult
Redflag AI · 2024–25

Cyclops watermarking

Patented
Problem

Pirated live streams need to be traced back to the account that leaked them.

Constraint

The mark must survive re-encoding, cropping and screen capture while staying invisible to viewers.

Approach

Led the R&D of a watermarking algorithm combining signal processing, computer vision and ML decoding, and built most of the low-latency streaming backend around it.

Result

Industry-leading decode robustness. Infrastructure cost cut by about 40% and compute by about 90% while usage tripled.

Optikka · 2025–

AI-integrated media platform

Problem

A major sports broadcaster needed AI built into its production workflow.

Constraint

Four months to delivery, on infrastructure that had to be auditable and finely permissioned.

Approach

Sole architect of 450+ Terraform-managed AWS resources, a relationship-based permission system and a GPU-bound ML image pipeline.

Result

Delivered on time and now part of the client's daily workflow.

Optikka · 2025–

Fine-grained permission system

Problem

Enterprise clients need access rules finer than roles: per entity, per scope, and across accounts.

Constraint

Roles, groups, inheritance and single sign-on all have to compose, and permission checks still have to be fast.

Approach

An IAM-like, relationship-based model on OpenFGA and DynamoDB with policy-based roles, scope inheritance, group membership and cross-account sharing.

Result

One permission layer behind every part of the platform, including SSO.

Optikka · 2025–

Standards that coding agents follow

Agentic engineering
Problem

Engineering standards written for people do not reach the AI coding agents that now write much of the code.

Constraint

Every rule has to be specific enough for an agent to apply and for a check to verify.

Approach

Rebuilt 33 design and standards documents as a rule system: about 100 rule IDs across 10+ domains, each with a severity, the file paths it covers and how it is enforced (lint, CI or AI review).

Result

One set of standards that people and agents both read, apply and are checked against.

Optikka · 2025–

Audit-log query engine

Problem

Operators needed to ask plain-language questions of a large audit history.

Constraint

Answers in seconds, at a cost per query that stays negligible as the log grows.

Approach

Retrieval-augmented generation with prompt size held constant regardless of history length.

Result

Sub-10-second answers at a fraction of a cent per query.

Solo founder · 2025–

Interactive-canvas platform

Problem

Teaching material needs to be annotated, organised and searched directly on a canvas.

Constraint

One person building every layer, from schema and infrastructure to interface, pricing and go-to-market.

Approach

A custom camera system, SVG annotation primitives with keyboard-driven placement, semantic search with synonym expansion, and tiered content gating.

Result

In development, with infrastructure cost modelled across three scaling scenarios.

Personal · 2023 · hand-coded, pre-AI

MusicMark

Bridge projectSource ↗ for MusicMark on GitHub (opens in a new tab)
Problem

Writing fingerings into a score is slow, and for music like Opus Clavicembalisticum it takes days. There is no dataset that pairs notes with the fingerings pianists actually use.

Constraint

No labelled data. Each fingering depends on the fingers just used and the notes still to come, and the two hands mirror each other.

Approach

Generated the training data from music theory: every scale mode and arpeggio inversion with comfort-optimised fingerings, extended by weighted random walks over a transition map. A two-layer GRU per hand (PyTorch) with circular pitch encoding feeds its own predictions back as input. Reads and writes MusicXML.

Result

80–90% validation accuracy; fingers a Bach fugue in under half a second.

Personal · 2023 · hand-coded, pre-AI

FugueStat

Bridge projectSource ↗ for FugueStat on GitHub (opens in a new tab)
Problem

Finding every subject entry by hand in fugues that run from ten minutes to two hours, as Sorabji's do.

Constraint

Entries are transposed, partial or altered, and may be reversed, inverted, augmented or diminished.

Approach

Fuzzy matching on intervals and durations with a custom edit distance (costs for contracted intervals, inserted or dropped notes, and rests), a sliding window that trims each match from both ends, and weighted interval scheduling to choose the best non-overlapping matches across transformations.

Result

Marks subject entries and five transformations directly in the MusicXML score, in roughly linear time in the length of each voice.

Watermarking pipelineA mark is embedded per viewer at ingest, survives streaming, re-encoding and screen capture, and is decoded from a pirated copy to trace its source.FIG. 1 · SCHEMATIC, NOT TO SCALEINGESTlive sourceEMBEDper-viewer markSTREAMCDN · low latencyCAPTUREre-encode · cropDECODEtrace the sourcethe mark must survive everything in between
Cyclops, the patented watermark behind the first dossier entry.

History

  1. 2025 – nowPrincipal EngineerOptikka (remote)
  2. 2025 – nowFounder & ArchitectInteractive-canvas SaaS, solo
  3. 2024 – 2025Software Engineer → SeniorRedflag AI, in eight months
  4. 2022Software Development Engineer IAmazon Web Services, Vancouver
  5. 2017 – 2022B.CS, Statistics minorUniversity of Waterloo, with six internships

Toolkit

Languages
Python · TypeScript · C++ · SQL · HCL · GraphQL
Cloud & infrastructure
AWS · Cloudflare · Terraform · Docker · Redis · RabbitMQ · OpenFGA · GitHub Actions
AI, vision & media
PyTorch · OpenCV · FFmpeg · LangChain · pgvector · HDBSCAN · Claude Code · MCP
Web
React · Next.js · FastAPI · React Query · Zustand