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Career Ledger

Career Ledger

Bell is where I'm focused now. Hopkins and UofT built the depth.

Ledger mapCareer lineage & dependencies
Drawn byS. Hossain
ScaleNTS
RevisionB
RefSH-CL-002
Lineage (time)
2026+
2025
2024
2023
2022
2021
2020
2019
2018
The pivot → CS + BioInfo
ABRCMS '23 · oral award
Harvard NCRC · plenary talk
BSc Hons · 3.95 major GPA
ABRCMS '24 · poster award
Named gatekeeper · 7 wk
Fig. 02.1Career lineage graph
4 nodes · 4 dependencies · 2018 → presentCareer Ledger · Quiet Systems · Rev B

Bell Canada · Data Engineer

June 2025 – Present

I own 25+ production data pipelines, including 14 scheduled control flows, behind field-operations and executive reporting.

$26.8Mmisreported order value corrected
28K+dropped records recovered
3.5Mduplicate rows removed

28K+ records, silently dropped. then recovered.

Role record
  • Own 25+ production data pipelines, including 14 scheduled control flows, behind field-operations and executive reporting: monitoring, incident response and change control; mentor teammates on debugging and root-cause analysis.
  • Corrected $26.8M of misreported order value in a $40M+/year pipeline: restored $4.1M under-counted (including $2.7M across 8,355 missing orders) and removed $22.7M double-counted, through a reversible production cutover with zero duplicate-key groups.
  • Owned a P1 incident on an executive KPI dashboard: reproduced it cell for cell from the fact table and isolated two opposite ETL defects across 13 sources; both fixes validated (mangled IDs from 13,445 to 0).
  • Built the 3-tier nightly batch ETL/ELT pipeline (staging, warehouse, analysis) on Teradata and SAS DI behind network-ticket reporting, integrating four systems into a 78-column fact table; 150K records/day since November 2025; presented to directors.
  • Technical lead for the team's first MongoDB-to-BigQuery migration pipeline on the GCP data platform: designed the scalable landing schema (partitioned, clustered keys plus a JSON payload; partition pruning for query cost optimization).
  • Wrote the pipeline's Terraform, Cloud Composer orchestration (DAGs) and Cloud Run ingestion jobs via GitLab CI/CD, with watermark-based change data capture (CDC) and MERGE upserts.
Show the full role record (12 more)Hide the extra 12 entries
  • Set technical direction: authored the approved high-level data architecture for a four-layer BigQuery data warehouse (landing, core data models with declared grains and schema-contract tests, data marts, semantic layer) and designed its nested-order unpacking, with a PySpark-versus-BigQuery SQL pilot planned.
  • Ran a large-scale backfill of 42M+ documents from 5 production MongoDB Atlas collections into a BigQuery dev dataset; caught a silent half-load by reconciling source counts, and fixed Airflow zombie tasks and out-of-memory batches.
  • Built and offline-tested a reliability hardening package for 5 Airflow DAGs (the watermark advances only after a successful MERGE, pre-merge validation, empty-batch no-ops): 16 behavioral tests and 42 static checks, now in code review.
  • Built a Python reconciliation toolset (value diff, ID-set diff, checkpoint-resumable row hashing via the BigQuery Storage Read API) and compared 6.09M rows across 5 tables on QA-sourced development data: 99.98% identical.
  • Cut a 23M-row join 83% (12 to 2 min) through performance tuning (filtered lookups, predicate pushdown, skew analysis) before go-live; traced a $10M gap in internal revenue reporting to one date filter.
  • Recovered 28K+ silently dropped records and grew usable history from 1 to 9+ months; removed 3.5M duplicate hierarchy rows with point-in-time SCD Type 2 joins.
  • Replaced a 1,000-line legacy SQL view with a 57-step SAS DI ETL (complex joins across 13 source tables) building order- and circuit-grain fact tables, surfacing 74 orders the old view dropped.
  • Took an automation-rate KPI from business requirements to build: verified the business rule across 3.39M interactions, rejected a defective draft SQL, and added the measure across 7 SAS DI jobs.
  • Root-caused missing billing addresses across 6 billing systems and won written business approval for the fix; accounts with a usable province rose 6.4x (147K to 947K).
  • Analytics engineering and BI: built a MicroStrategy Intelligent Cube (77 attributes, 12 metrics) for self-serve reporting, plus KPI dashboard data products released Dev to Prod; designed data quality alerting (freshness and volume checks, rolling P10/P90 thresholds).
  • Named change-control gatekeeper and peer reviewer 7 weeks in; facilitated weekly cross-functional stakeholder meetings; closed 157 of 170 tickets (92%, 72% P1/P2); set data governance and documentation standards (data dictionary, data lineage, metadata management, view-based access isolation for external accounts).
  • Use AI coding assistants (Claude, Gemini, ChatGPT) for pipeline scaffolding and SQL review; designed a Teradata history layer for LLM-generated quality scores (idempotent reloads, retention).
Read the recovery note: runbook, data diff, reconciliation →
how to read this

every entry links to the system it ran on and the numbers it produced.

Awards

Outside proof that the work held up in front of real review.

yearrecognitionissued byref
2024Poster Presentation AwardReceived top honors for a graduate-level poster presentation among 150+ graduate presenters on advancing open-source bioinformatics platforms.Annual Biomedical Research Conference for Minoritized Scientists (ABRCMS) - Graduate Division$2,500 travel awardproof ↗
2024Friends of Arts and Science AwardAwarded for academic excellence in Computer Sciences and Physical & Life Sciences during the 2023-2024 academic year.University of Toronto - Faculty of Arts & Science
2024Plenary SpeakerSelected as 1 of only 12 plenary speakers from over 5,000 national applicants. Delivered a keynote on integrating transcriptomics and proteomics data for glioblastoma research.National Collegiate Research Conference (NCRC) - Harvard Universityproof ↗
2024Poster PresentationPresented computational approaches for cancer biomarker identification using integrated multi-omics analysis and machine learning methodologies.National Collegiate Research Conference (NCRC) - Harvard Universityproof ↗
2023Oral Presentation AwardAwarded top presenter in the Computational and Systems Biology division, selected from 80 oral presenters at a conference with over 3,500 attendees.Annual Biomedical Research Conference for Minoritized Scientists (ABRCMS) - Computational and Systems Biology Division$2,500 travel awardproof ↗
2023Friends of Arts and Science AwardAwarded for academic excellence in Computer Sciences and Physical & Life Sciences during the 2022-2023 academic year.University of Toronto - Faculty of Arts & Science
2022Friends of Arts and Science AwardAwarded for academic excellence in Computer Sciences and Physical & Life Sciences during the 2021-2022 academic year.University of Toronto - Faculty of Arts & Science
Education

Strong CS and bioinformatics foundations, plus a lot of range.

University of Toronto

St. George Campus · Toronto, Ontario, Canada
Degree
Bachelor of Science (Honours)
Program
Bioinformatics & Computational Biology (joint program with Computer Science & Biochemistry)
Coursework
Algorithm Design & Analysis, Software Design, Theory of Computation, Probability & Statistics
Major GPA
3.95 / 4.0
Graduated
June 2024
Sabbir Hossain · Career LedgerPage 02