Ankit Kumar
Srivastava

1. Mar 2025 — Jun 2026 Mumbai, India

   Zeta Tech (Directi)

   Software Development Engineer — Java Backend

   • Rebuilt core payment-transaction services in Java and Spring Boot, backed by JUnit/Mockito test suites, cutting critical API response times by 30%.
   • Co-designed the payments microservices architecture with product and platform teams, reducing operational overhead by 40%.
   • Built PCI-DSS compliant data pipelines in Java processing 20M+ cardholder records, cutting batch reconciliation time from 6 hours to 2 in coordination with the compliance team.
   • Introduced Kafka event streaming and Redis caching in the core transaction path, cutting latency by 20% and database load by 35%.
   • Deployed and monitored Spring Boot services on Kubernetes with ELK-based observability, reducing infrastructure costs by 20%.

   Java · Spring Boot · JUnit/Mockito · Kafka · Redis · Kubernetes · ELK Stack · PCI-DSS

2. Feb 2023 — Mar 2025 Mumbai, India

   Netcore Cloud

   Software Engineer — Java Backend

   • Led a cross-functional team of five building Java and Spring Boot microservices, owning sprint planning, code reviews, and releases — cut downtime by 40%.
   • Tuned SQL queries and Hibernate/JPA mappings across core services, boosting application performance by 30%.
   • Set up Maven-based CI/CD pipelines with Jenkins and GitHub Actions, cutting deployment time by 50%.
   • Integrated OAuth 2.0 and JWT-based authentication into the Java backend, cutting average authentication time from 5s to 2s.

   Java · Spring Boot · Hibernate/JPA · Maven · Jenkins · GitHub Actions · OAuth 2.0 · JWT

3. Jan 2022 — Aug 2022 Chandigarh, Mohali, India

   Zscaler

   Software Engineer Intern

   • Executed core components of a legacy-to-cloud migration, improving access speed by 40% for 100+ users with minimal downtime.
   • Designed encryption methods and 100+ test scenarios with the QA/security team, achieving a 99% success rate securing data for 200+ users.

   Python · Shell Scripting · Selenium · Pytest · AWS

4. Jul 2021 — Jan 2022 Delhi, India

   Sunrise Mentors Pvt. Ltd.

   Teaching Assistant, EdTech Platform

   • Mentored 500+ students and led a 15-member TA team across 25 web development projects, standardizing code-review feedback.

   Python · Java · C++ · Web Development · Mentorship

Flagship work in distributed systems, data engineering, backend, and enterprise AI — the rest is one scroll further down.

Distributed Job Scheduler Systems

A scheduler in the spirit of Quartz, Kubernetes Cron, and Airflow, built to handle recurring and delayed jobs at horizontal scale with exactly-once claims.

• Leader-elected cron materialization; all-active workers compete on a Redis priority queue.
• Exactly-once claim via Redis lock + Postgres status transition + unique execution token.
• Retries with exponential backoff, dead-letter queue, heartbeat-based failure recovery; HLD + LLD docs in-repo.

Java 21 · Spring Boot · Postgres · Redis · Kafka · Docker Compose · Flyway

View source ↗ HLD ↗ LLD ↗

Notification Platform Systems

A multi-channel notification service covering Email, SMS, WhatsApp, Push, and Slack, built on real infrastructure instead of in-memory stubs.

• Kafka-backed ingress with an in-process priority queue, scheduled sends, and a DB + Kafka DLQ for exhausted retries.
• Redis-enforced idempotency keys and rate limiting, with exponential backoff on failed deliveries.
• Template rendering, delivery analytics, and a local provider inbox for non-email channels; SMTP → MailHog for email.

Java 21 · Spring Boot 3 · Postgres · Redis · Kafka · MailHog · Flyway · Docker Compose

View source ↗ HLD ↗ LLD ↗

API Gateway Systems

A production-style API gateway with JWT auth, rate limiting, circuit breaking, and observability, built as a custom filter pipeline instead of a Spring Cloud Gateway config dump.

• Chain-of-Responsibility filter pipeline: observability → routing → auth → rate limit → circuit breaker + proxy.
• HS256 JWT auth with per-route role checks; Token Bucket / Sliding Window rate limiting, in-memory or Redis Lua for distributed limits.
• Per-route CLOSED → OPEN → HALF_OPEN circuit breaker; correlation IDs and Micrometer/Prometheus metrics throughout.

Java 21 · Spring Boot 3.4 · JJWT · Redis · Micrometer · Prometheus

View source ↗ HLD ↗ LLD ↗

Event-Driven E-commerce Backend Kafka

Distributed checkout across order, inventory, payment, and notification services over Kafka.

• Multi-service architecture with async Kafka workflows for reliable checkout.
• Transactional outbox, saga-style orchestration, and idempotency for safe retries.
• Docker Compose local stack plus Kubernetes deployment assets for portfolio demos.

Java · Spring Boot · Kafka · Microservices · Outbox · Saga · Docker · Kubernetes

View source ↗ Docs ↗

StreamPulse Kafka

A real-time e-commerce analytics pipeline covering Kafka ingestion, windowed stream processing, ClickHouse OLAP, and a live dashboard.

• Tumbling and session windows (Flink-style, with optional Flink SQL) computing per-minute revenue, volume, and conversion metrics.
• Real-time fraud rules covering purchase velocity, high-value transactions, and geo-mismatch checks, with a dead-letter queue for invalid events.
• ClickHouse modeling with MergeTree/ReplacingMergeTree, TTL, and materialized views; FastAPI + React dashboard polling every 4s.

Kafka · Flink · ClickHouse · FastAPI · React · Docker Compose

View source ↗ HLD ↗ LLD ↗

Mini Elasticsearch Search

I wanted to actually understand how a search engine works under the hood, so I built a small one myself. No Lucene, no Elasticsearch library, just the core ideas coded from scratch.

• Wrote my own inverted index and ranked results with BM25 and TF-IDF instead of just doing keyword matching.
• Added a trie for autocomplete, handled synonyms, and highlighted matched terms in the results.
• Split the index across shards (routed by hashing the doc id) and query all of them in parallel, then merge the results.

Python · FastAPI · Inverted Index · BM25 · TF-IDF · Distributed Sharding

View source ↗

Mini Redis Systems

I've used Redis for caching more times than I can count at work, but I never actually built one myself. So I sat down and wrote a small version in Java, starting from basic eviction and working all the way up to cluster routing.

• Wrote my own LRU eviction and TTL expiry for the core cache, then added RDB style snapshots and an AOF log so a restart doesn't wipe the data.
• Consistent hashing with virtual nodes routes keys across shards through a ClusterManager, so scaling out just means adding another shard node.
• Leader and follower replication plus pub/sub sit on top of the same cache core instead of being bolted on as an afterthought.

Java 21 · LRU Eviction · TTL · RDB/AOF Persistence · Leader-Follower Replication · Consistent Hashing · Pub/Sub

View source ↗ HLD ↗ LLD ↗

Uber Backend Systems

I always wondered how an app like Uber actually finds you a driver in real time, so I built the backend for that myself. Just the ride-hailing logic, no frontend needed.

• Track live driver locations with Redis GEO and match riders to the nearest free driver, guarding the claim with a putIfAbsent so two riders can never end up with the same driver.
• Modeled the whole trip as a real state machine — you can't jump straight from MATCHED to COMPLETED, every status change gets validated.
• Surge pricing reacts per geohash cell based on actual demand vs supply, and Kafka carries location/trip/notification events end-to-end into a WebSocket that pushes live trip updates to the rider.

Java 21 · Spring Boot · Redis GEO · Kafka · WebSocket · Docker Compose

View source ↗

FocusTodo Collab Todos

A full-stack todo app with shareable realtime rooms, using REST for CRUD and STOMP/WebSocket for live sync.

• Excalidraw-style share links so multiple browsers edit the same list live.
• Optimistic locking via @Version (409 on conflict) so concurrent edits don't silently overwrite.
• One-command local run with Docker Compose, plus Postman collection and Swagger UI.

Java 21 · Spring Boot 3 · React (Vite) · MongoDB · STOMP/SockJS · Docker Compose

View source ↗

Real-Time UPI Analytics Platform

A complete data engineering pipeline for real-time UPI transaction analytics, from ingestion all the way to dashboards.

• Kafka ingestion with Flink for real-time validation and cleaning.
• dbt transformation models plus Airflow DAGs for daily batch aggregations.
• Grafana dashboards for real-time visualization, fully containerized with Docker Compose.

Kafka · Flink (Java) · Airflow · PostgreSQL · dbt · Grafana · Python · Docker

View source ↗

Enterprise RAG Intelligence Platform

An enterprise AI assistant with role based access control, hybrid retrieval, and knowledge graph reasoning, designed to plug into a company's existing systems.

• Hybrid retrieval — dense (BGE + Qdrant) and sparse (BM25 + Elasticsearch) — with cross-encoder reranking.
• Retrieval-time role filtering and PII/secret blocking for unauthorized roles.
• Knowledge-graph multi-hop reasoning with NetworkX; JWT auth, audit logs, RAGAS eval, Langfuse/Phoenix tracing.

FastAPI · Streamlit · Qdrant · Elasticsearch · BGE Embeddings · NetworkX · Docker

View source ↗

PII Masking API Go

Stateless Go microservice masking PAN, Aadhaar, phone, email, and GSTIN before logs or downstream systems see raw data.

• Single mask, bulk mask, validate-only, and auto-detect endpoints.
• Format validation before masking — invalid input returns 400, not partial leaks.
• Stateless, no database dependency — runs behind a gateway or as a sidecar.

Go · net/http · Docker · Regex validation

View source ↗

PDF Toolbox API Go

A Go microservice for merge, split, compress, encrypt, and convert, with outputs landing on Cloudflare R2 with a public URL.

• Multi-endpoint processing: merge, split, compress, encrypt/decrypt, doc-to-PDF.
• Containerized with qpdf, ghostscript, poppler-utils, and LibreOffice.
• Deployed on Railway with environment-aware config.

Go · pdfcpu · qpdf · LibreOffice · Docker · Cloudflare R2 · Railway

View source ↗