Backend Engineer

Project.

01) 청건부산 2nd Website.

Mobile-exclusive website for the 16th Together Festival and the Cheonggeon Busan 2nd event.

Description.

As the lead developer for this project, which I managed for the second consecutive year,
I was responsible for a service providing event information and activity visualization to 4,200 Daily Active Users (DAU) in Busan.
I collaborated with an illustrator and the event committee to develop the website.
I implemented APIs suited to the event planning and interactive content,
while also handling front-end and DevOps tasks within the given environment and resources.

What did I do.

  • Developed an API server running 32 APIs.
  • Implemented a booth activity visualization game called Zero Game.
  • Developed a cookie-based user and staff registration and authentication system.
  • Built a custom server logging system.
  • Designed and implemented all necessary front-end, UI, and ERD.
  • Communicated with external stakeholders regarding project status, requirements, and planning.

Hyperlink.

02) DID and ZKP-Based Identity Verification System.

A Web3 identity verification system implemented using Decentralized Identifiers (DID) and Zero-Knowledge Proofs (ZKP).

  • Graduation Project, Pusan National University, 2023

  • 2024.03 ~ 2024.06

Description.

This project aimed to move away from traditional centralized DB by implementing a DID protocol that aligns with Web3 standards.
Utilized the Near Smart Contract platform to implement the DID protocol and Snark.js library to build the ZKP circuit.
The system verifies the identity of Pusan National University students through a custom-built Chrome Extension Wallet.
Both the FE and BE communicate with a blockchain server, ensuring that no personal data is stored in a centralized DB while performing student identity verification.

What did I do.

  • Designed the infrastructure and managed the DB.
  • Developed Holder, Issuer, Verifier, and Server API servers.
  • Implemented server-blockchain network communication using the Snark.js library.

Hyperlink.

03) Ontact Korea Service.

A parcel forwarding service for international customers shipping Korean goods abroad.

  • Outsourced project for (주)에버스톤

  • 4-month internship at Pusan National University, practical experience program

  • 2024.03 ~ 2024.06

Description.

This service, used by around 4,600 users across 195 countries, launched officially in June 2024 after a 4-month development period.
Users primarily use the platform for purchase and shipping forwarding services.
The admin page allows handling of requests by providing quotes and visualizing internal warehouse management.
The service supports international payments via PayPal for four external carriers (FedEx, UPS, etc.).

What did I do.

  • Developed coupon service, review, and announcement features using 무신사 and 오늘의 집 as references.
  • Utilized open APIs from FedEx, UPS, and others to calculate international shipping rates.
  • Implemented payment, refund, and partial refund transactions using the PayPal API.
  • Built a database backup system scheduled to run at specific times.
  • Created middleware for image compression and to unify various time zones into UTC.
  • Led the initial deployment of the service using docker-compose and implemented SSL certificate renewal.
  • Refactored the existing website to be optimized for mobile users.
  • Managed UI components using Figma.
  • Introduced Flow collaboration tool for managing development timelines and maintenance.
  • Communicated with foreign customer service staff within the outsourcing company.

Hyperlink.

04) 청건부산 1st Website.

Mobile-exclusive website for the 15th Together Festival and Cheonggeon Busan 1st event.

Description.

This service provided event information for a Busan event with 1,700 Daily Active Users (DAU).
I collaborated with event planners and the committee to develop the website.
I developed two API servers: one for content and one for a game, and set up the necessary front-end and cloud infrastructure.

As the sole developer, I implemented the required front-end and DevOps infrastructure by referencing and learning from minimal resources as needed.

What did I do.

  • Developed an API server running 14 APIs.
  • Created a team-based board game service using dice.
  • Implemented a QR code-based system for user team creation and participation.
  • Built a staff authentication system using LocalStorage to reduce API traffic.
  • Developed a custom server logging system.
  • Implemented zero-downtime deployment using pm2 with multi-process architecture.

Hyperlink.

05) Fitory.

A PWA service that tracks workout records with social features, displaying your three main lifts (bench press, squat, deadlift) ranked and tiered among users of similar weight classes.

  • Team project for Naver Boostcamp Web & Mobile 7th cohort

  • 2022.11 ~ 2022.12

Description.

Fitory is a workout tracking and social networking service designed to motivate users by visualizing their exercise data.
The project was developed and deployed by a team of 2 FE and 2 BE developers.
As this was my first team project, I gained experience in establishing a development culture, including Git conventions,
Figma-based planning, and writing API specifications.

What did I do.

  • Developed an API server running 28 APIs.
  • Built an SNS notification system using Server-Sent Events (SSE).
  • Optimized performance of statistical APIs for workout data using Multi-Column Indexing.
  • Developed a file compression and storage pipe for user-uploaded photos using Nest.js.
  • Conducted API performance testing and refactored CPU-intensive code using k6 and Clinic.js.

Hyperlink.

Skill.

Communication.

  • I believe it’s important not to make assumptions or passively react to requirements or specific functionalities.
  • I strive to confirm the intent behind any suggestions, as I am cautious about the potential side effects of giving up communication due to fear of my opinions not being implemented.
  • I believe that clear code and transparent communication come from a well-rested mind.

Node.js.

  • Proficient in using Node.js to implement efficient asynchronous processing and event-driven architecture.
  • Capable of designing and building RESTful APIs using key frameworks like Express.js.
  • Experienced in developing interactive web applications by implementing real-time data communication using WebSocket.

Nest.js.

  • Able to write API test code using Testing Library.
  • Understand the Nest.js lifecycle and MVC architecture, allowing for the implementation of Guards, Interceptors, and Pipes based on use cases.
  • Skilled in proper dependency injection to reduce coupling and perform module-level testing.
  • Experienced in safely interacting with databases using DTO and ORM.

Database.

  • Capable of selecting NoSQL or RDB based on service requirements and read/write performance needs.
  • Able to design ERDs and determine the need for table normalization through scenario testing.
  • Skilled in measuring query cost through various scan methods and applying single or multi-column indexing.
  • Experienced in implementing pre- and post-processing of data requests using MySQL Triggers.

DevOps.

  • Proficient in setting up web infrastructure using Nginx, ACG, and Cloud DB in a cloud environment.
  • Experienced in implementing zero-downtime deployments in a multi-process environment using tools like pm2.

Contact.