Yohanes Sefrianto Laga Keraf

About

I build the systems behind the product — and the dashboards that explain them.

Skills

Range across the whole data & software stack.

Experience

A path through software, data, and AI.

1. Data Analyst Assistant Manager

   Jun 2026 — Present

   PT. Central Proteina Prima, Tbk

   Partnering across Finance, Operations, and Supply Chain to turn cross-divisional data into decisions leadership can act on.

   • Partner with Finance, Operations, and Supply Chain to translate operational datasets into actionable business insights
   • Design, develop, and maintain centralized BI dashboards tracking cross-departmental KPIs, resource utilization, and performance metrics
   • Conduct data-driven audits to identify operational bottlenecks, cost-saving opportunities, and efficiency gaps
   • Architect scalable data models and automated reporting workflows (SQL, Python, BI tools) to eliminate manual work and ensure data integrity
   • Act as internal data consultant to non-technical division heads, helping define data requirements for strategic planning

2. Data Analyst Assistant Manager

   Jul 2023 — Jun 2026

   PT. Sentral Retailindo Dewata

   Owned analytics for a supermarket chain — from raw POS data to the dashboards and forecasts that shaped pricing, inventory, and marketing decisions.

   • Consolidated data from POS systems, loyalty programs, and cross-department sources (inventory, suppliers, employee productivity) into analysis-ready datasets
   • Applied statistical analysis in Excel, SQL, Python, and R for sales forecasting, customer segmentation, and market basket analysis
   • Built and maintained KPI dashboards tracking sales growth, customer retention, inventory turnover, and operational efficiency
   • Evaluated the impact of pricing strategies and promotional campaigns on sales and profitability
   • Forecasted demand from historical trends to improve inventory planning and avoid stockouts or overstocking
   • Presented findings to management, marketing, and operations stakeholders to support data-driven decision-making

3. Data Analyst

   May 2018 — Feb 2023

   JD.ID

   Built the SQL-driven reporting and data mart backbone behind strategic decisions at a major e-commerce platform.

   • Built SQL-based data processing pipelines to produce reports and analytics supporting strategic decisions
   • Designed data marts to optimize operational performance
   • Explored large-scale data to surface actionable business insights
   • Developed ongoing and ad-hoc reports to track key performance metrics
   • Supported internal and external stakeholders in understanding and interpreting data and analysis

4. IT Executive

   Jul 2015 — May 2018

   Everbest Shoes Indonesia

   Kept retail operations running — from ERP troubleshooting to the sales and stock reports the business ran on.

   • Troubleshot and resolved operational issues on the ERP system (ETP) across store front-end and back-office
   • Built custom reporting applications and reporting services
   • Configured promotion schemes within the system
   • Administered databases using SQL
   • Produced biweekly sales reports and weekly stock reports

5. Senior Staff — Data Analyst

   Mar 2014 — Jul 2015

   PT Malindo Feedmill Tbk

   Turned raw operational data into statistically grounded reports and process improvements.

   • Interpreted data and analyzed results using statistical techniques, delivering ongoing reports
   • Designed data collection systems and strategies to improve statistical efficiency and data quality
   • Identified and interpreted trends and patterns across complex datasets
   • Cleaned data and reviewed reports and performance indicators to catch and correct errors
   • Partnered with management to prioritize business and information needs and identify process improvements

6. IT Freelancer

   Jul 2013 — Mar 2014

   Freelancer

   Independent IT and data support work for small businesses and personal clients.

7. IT Staff — Project Support, Assessment Division

   Apr 2009 — Jul 2013

   PPM Institute of Management

   Started my career in IT infrastructure and web application administration for a management institute's assessment division.

   • Administered the e-recruitment website, managing database updates and announcements
   • Processed e-recruitment data using Excel and Access
   • Maintained LAN infrastructure and troubleshot hardware/software issues
   • Administered web-based assessment tools (Harrison Assessment psychometric testing)
   • Supported IT infrastructure division project needs, including interview recording/editing for client reporting

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Certifications

Continuous, structured learning.

Tech Stack

Tools I reach for daily.

Python

JavaScript

TypeScript

PHP

Laravel

Node.js

Docker

Git

GitHub

BigQuery

SQL Server

MySQL

PostgreSQL

n8n

OpenAI

Claude

Gemini

GitHub Statistics

What the commit history says.

Contribution Activity