Open to senior backend roles

Avi
Sihag

4 years, 4 completely different stacks. Ride-hailing distributed systems, mobile apps in Flutter, quick-commerce backend, blockchain infra. IIT Delhi EE. Founding engineer twice over.

Portfolio Email LinkedIn
Stack Go Python Dart / Flutter TypeScript Kafka GCP AWS LangChain
system.events — events
real-time simulation ~0.3 ev/s
Career

Work Experience

Production systems at scale — different domain, different stack, every year.

Senior Software Engineer
04/2025 – Present
Mrsool — Ride Hailing Platform, Saudi Arabia
  • Among 3 founding engineers who built Mrsool's ride-hailing platform from 0→1 in under 6 months; peak 5,500+ completed trips/day, 10,000+ drivers, 145,000+ customers.
  • Architected trip lifecycle state machine (request → dispatch → enroute → arrival → settlement) with cross-service orchestration; underpins 385,000+ trip transactions.
  • Sole author of real-time bidirectional chat — RFC to production: Kafka + Redis Streams + ScyllaDB; idempotent delivery, event replay, stateless reconnection.
  • Integrated HyperPay with instrument tokenisation; 7,400+ instruments across 6,500+ users, coupled to fare settlement lifecycle.
  • Built fraud detection across 5 heuristic signals — surfaced 9,000+ flagged trips (2.3% of platform volume).
  • Shipped customer blocking (JTI rotation), penalty reversal with GPS no-show verification and atomic billing rollback.
  • Architected Butler 2.0 — LLM-powered conversational commerce; stateless Go/Node.js WebSocket gateway, NATS JetStream, Redis sessions, LangChain + GPT-4.
GoKafkaRedis Streams ScyllaDBNATS/JetStreamPostgreSQL gRPCHyperPayLangChain GPT-4K8sGCP
Founding Engineer
09/2023 – 03/2025
Adora Inc., Japan
  • Built parental control and child safety app with 4-person team — 30K+ MAU, 100K+ installs across Japan, Korea, English-speaking markets.
  • Raised crash-free rate from 40% to 95%; integrated Shorebird cutting patch release time by 40%; battery optimisations reduced power consumption 45%.
  • Shipped Unsafe Text Detection, Purchase Blocking, Line Voom Block; Korean localisation; Intercom migration (25% issue resolution boost, 15% drop-off reduction).
  • Firebase & GCP infra including Cloud Functions; CI/CD (Codemagic) for simultaneous prod/stage/dev builds.
FlutterDartTypeScript FirebaseGCPShorebirdAmplitude
SDE-1 — Fullstack Engineer
07/2022 – 03/2023
Blinkit (Zomato)
  • Catalogue Management: cached Django APIs for downstream microservices; React frontend for content team with onboarding automation.
  • Print-as-a-Service: end-to-end across backend, Android app, and internal services — launched at 600 avg daily orders across 5 dark-store polygons in 2 cities.
DjangoPythonReactPostgreSQL
Backend Engineer (Freelance)
06/2023 – 08/2023
Golom — Blockchain NFT Marketplace
  • Cached Django APIs with rate-limited streaming; deployed Polygon node, ElasticSearch cluster, InfluxDB on custom AWS AMIs.
DjangoAWSElasticSearchSolidity
Expertise

Technical Skills

Different domain, different stack, every year. Breadth by necessity.

Stack journey · 4 years · 4 domains
2022Blinkit (Zomato)
PythonDjangoReactPostgreSQLAndroidRedis
2023Golom · Freelance
DjangoAWSElasticSearchInfluxDBSolidityDocker
2023–25Adora Inc., Japan
DartFlutterTypeScriptFirebaseGCPShorebird
2025 →Mrsool, Saudi Arabia
GoKafkaScyllaDBNATSRedisLangChainK8s
LIVE
—
days at Mrsool
0
trips since you loaded
—
chat msgs delivered today
100%
platform uptime
trip_fsm.go Go

      


      
      

        
realtime chat · simplified

        

          
Driver

          

          
Kafka

          

          
Redis

          

          
Customer

        

        

          ↓ ScyllaDB (persist + replay)

          idempotent · stateless gateway

          last-ack offset reconnect
        

      


    

  








  

    

      Systems
      
System Architecture

      
Interactive diagrams of two systems designed and built from scratch. Hover nodes for details.

    


    

      
      
    


    
    

      

        

          Sole designer + implementer. Bidirectional driver↔customer messaging — RFC to production.
          Kafka for durable event log, Redis Streams for low-latency fan-out, ScyllaDB for persistence + replay.
          Stateless gateway design → horizontally scalable with zero sticky sessions.
        

        
        

          

            📱
            
Driver App

            
WebSocket

          

          

            ws
            

          

          

            ⚡
            
WS Gateway

            
Go / Node.js

          

          

            produce
            

          

          

            📨
            
Kafka

            
topic per trip

          

          

            consume
            

          

          

            🔴
            
Redis Streams

            
fan-out

          

          

            subscribe
            

          

          

            ⚡
            
WS Gateway

            
Go / Node.js

          

          

            ws
            

          

          

            📱
            
Customer App

            
WebSocket

          

        

        
        

          Kafka consumer also writes → ScyllaDB (TTL-based persistence, dedup via msg_id, replay on reconnect)  · 
          Idempotent delivery via unique msg_id  · 
          Mobile reconnect replays from last-ack offset
        

      

    


    
    

      

        

          Sole designer + implementer. End-to-end trip lifecycle state machine.
          Atomic transitions with PostgreSQL advisory locks, gRPC fan-out to downstream services at each state,
          event emission for billing, notifications, and fraud scoring pipelines.
        

        

          

            
REQUESTED

          

          
▶

          

            
DISPATCH

          

          
▶

          

            
ENROUTE

          

          
▶

          

            
ARRIVED

          

          
▶

          

            
IN_TRIP

          

          
▶

          

            
COMPLETED

          

          
▶

          

            
SETTLED

          

        

        

          Any state → CANCELLED  · 
          Advisory lock per trip_id prevents race conditions  · 
          Each transition emits events → billing · fraud · notifications  · 
          Idempotent transitions → safe to retry
        

      

    

  








  

    

      Work
      
Selected Projects

    

    

      

        
🧠

        
Dynamic Facial Emotion Recognition

        
Sep 2021 – Dec 2021 · Prof. Tapan Kumar Gandhi, IIT Delhi

        
Extended Part-Based Ensemble network from static images to video in unconstrained environments. Time Distributed CNN-LSTM on CK+ / MMI datasets.

      

      

        
📱

        
WhatsApp Dialer Automation

        
Mar 2021 – May 2021 · Freelance (CellularPartner)

        
Flask backend + Python/AutoIt automation to connect WhatsApp calls on demand. Call-stats API logging to MySQL for analytics.

      

    

  








  

    

      Documents
      
Portfolio Viewer

      
Resume and system design deep-dives for every Mrsool system built.

    

    

      
      
    

    

      

        

          
Avi_Sihag_Resume_Final_2026.pdf Senior Software Engineer

          

            ⬇ Download
            ↗ Open Tab
          

        

        
      

    

    

      

    

  








  

    

      Background
      
Education & Achievements

    

    

      

        

          
B.Tech, Electrical Engineering

          
Indian Institute of Technology Delhi

          
2018 – 2022

        

      

      

        
KVPY 2017 SX Scholar — selected by IISc Bangalore under Dept. of Science & Technology, Govt. of India.

        
Enactus IIT Delhi — Semi-Finalist, World Cup 2019 (San Jose, USA) among 36 countries; Winner, National 2019 among 109 colleges; Empressario B-Plan winner, IIT KGP (₹1L prize).

        
Technical Coordinator, Student Incubation Cell, IITD [2020–21] — built official club website in MERN stack.

        
Weightlifting Vice Captain, Vindhyachal Hostel, IIT Delhi [2019–20].

      

    

  








  

    

      
Let's build something great

      
Open to senior backend / distributed systems roles.
Happy to discuss architecture, systems design, or LLM infra.

      

        
          
          avisihag9919@gmail.com
        
        
          
          LinkedIn
        
        
      

    

  










  

    

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      avi@avisihag.com — bash
    

    

    

      avi@portfolio:~$