Impactful Work/Preparation Street - AI-Era Tech Preparation Platform
Preparation Street - AI-Era Tech Preparation Platform
16 technologies · 9 highlights
What I Built
- Founded and built PreparationStreet - my own AI-era-ready tech preparation platform - end to end as founder and sole architect: product, frontend, backend, payments, AI and operations. It runs three revenue products - TRISHUL (structured self-paced learning paths), FTM (Full-Time Personalized Mentorship) and 1:1 Mentorship (bookable expert sessions) - has generated $8,200 USD in revenue, serves 2K+ daily active users, and sits on a community of 40K+ engineers mentored.
- Designed TRISHUL as four certified learning paths - AI Architect, Everything About System Design, Algorithm Accelerator and Everything About DSA - plus a free 150 Problem Sheet as the top-of-funnel entry: each path is modelled as Product → Section → Topic → Question / Project with per-user progress, todo and activity tracking, so a learner always resumes exactly where they stopped and every completed item feeds a daily activity heatmap.
- Built FTM (Full-Time Personalized Mentorship) as tiered programs - 3 Month Sprint, 6 Month Transformation and 12 Month Mastery - where a purchase bundles Elite TRISHUL access as a separate entitlement recorded on the purchase itself, so access is granted exactly once and is auditable; a free trial session is gated by a single server-side eligibility service (no active FTM, trial not already used, and a cancelled booking does not burn the trial), so the rule cannot be bypassed from the client.
- Shipped 1:1 Mentorship booking on a weekly slot-availability model stored in UTC: a slot's absolute start is computed from the booked day plus its UTC start time, so past slots are rejected at booking time regardless of the visitor's timezone; an already-taken slot returns a clear "pick a different time" reason, and a unique index plus an E11000 guard turns a simultaneous double-booking race into one winner and one clean rejection instead of two confirmed sessions.
- Built a regional pricing engine as the single place any product decides what to charge: visitors in India see an INR price book billed in INR, visitors abroad see a USD price book billed in their own currency via geo-IP detection and cross-rate FX, and amounts are rounded even when no conversion happens so the quoted and charged figures match to the cent; FX rates are cached with a TTL, fall back to the last good rates and then to safe defaults, and support admin-pinned manual rates - so a rates-provider outage can never break checkout. Per-user custom pricing for TRISHUL and FTM sits on top for scholarships and partner deals.
- Engineered payment correctness on Razorpay end to end: orders are created server-side, client confirmation is verified with an HMAC-SHA256 signature and an owner check (only the buyer can verify their own payment), and a single webhook endpoint verifies the signature on the raw body and routes by order type to the FTM, mentorship or product handler. Because the verify call and the webhook race each other, fulfilment is idempotent by construction - a unique index makes the loser hit E11000 and return the winner's document - so a payment is fulfilled exactly once, never twice and never zero times.
- Added AI to the preparation loop: an in-product assistant answers questions with Claude on AWS Bedrock and Google Gemini, grounded through a RAG layer with metadata filters over the platform's own curriculum, with chat sessions, history and per-session context persisted per user - so a learner gets answers tied to the path they are actually on, not generic LLM output.
- Issued verifiable certificates for every TRISHUL path, the 150 Problem Sheet and FTM: each one carries a credential id in the form
PS-<CODE>-<random>generated from a cryptographically random source, issuance is idempotent (bulk inserts tolerate duplicate-key collisions and regenerate an id on a clash with bounded retries), and a TRISHUL Master certificate is awarded once all four paths are complete - turning progress into a shareable, checkable credential. - Ran the platform like a business, not a side project: an admin console with stats and time-series, user management, TRISHUL / FTM access grants, payments, slot management, pricing and custom pricing, listings and an append-only admin audit log; transactional email over AWS SES and Azure Communication Email (OTP, payment receipts, booking and trial confirmations, server alerts); a health/status page; and a hardened API behind helmet, compression, a CORS allowlist, an Origin guard and an internal-key guard, with Google / GitHub OAuth and JWT auth via Passport.
Tech Stack
Next.js 14 (App Router)React + TypeScriptTailwind CSS + Framer MotionZustand (client state)Recharts (progress analytics + heatmaps)jsPDF + html-to-image (certificates)Node.js + Express.jsMongoDB + Mongoose (~35 models)Razorpay (orders, HMAC verify, webhooks)geoip-lite + FX cross-rates (regional pricing)Claude on AWS Bedrock + Google GeminiRAG with metadata filtersPassport.js (JWT, Google OAuth, GitHub OAuth)AWS SES + Azure Communication Emailhelmet + compression + CORS / Origin / internal-key guardsWinston logging + health/status page
Key Concepts
- Founder-Built AI-Era Tech Preparation Platform - Three Revenue Products
- TRISHUL: Four Certified Paths (AI Architect, System Design, Algorithms, DSA) + Free 150 Sheet
- FTM: 3 / 6 / 12 Month Tiers With Bundled Elite TRISHUL Entitlement
- 1:1 Mentorship: UTC Slot Model, Past-Slot Rejection, Unique-Index Double-Booking Guard
- Regional Pricing Engine - INR Book in India, USD Book in Local Currency Abroad
- Idempotent Payments: HMAC Verify + Webhook Race Resolved by E11000 → Exactly-Once Fulfilment
- Server-Side Trial Eligibility - Cancelled Bookings Never Burn the Trial
- FX Resilience: TTL Cache → Last Good Rates → Safe Defaults → Admin-Pinned Rates
- AI Assistant on Claude (Bedrock) + Gemini Grounded by Curriculum RAG
- Cryptographically Random, Idempotent Certificate Credentials (PS-CODE-xxxx)
- Product → Section → Topic → Question Model With Per-User Progress + Activity Heatmap
- Admin Console With Append-Only Audit Log + Custom Pricing
- 4-Layer API Perimeter: helmet/CORS → Origin Guard → Internal Key → JWT
Low-Level Architecture (LLD)
High-Level Architecture (HLD)
Impact
- Generated $8,200 USD in revenue as a founder-built, bootstrapped product - designed, coded, priced and operated end to end by one engineer - across three products: TRISHUL, FTM and 1:1 Mentorship.
- Grew to 2K+ daily active users on top of a community of 40K+ engineers mentored, turning years of mentorship into a structured, self-serve product that keeps working while I am not in the room.
- Made checkout globally sellable from day one: India pays in INR from an INR book, the rest of the world pays in their own currency from a USD book, with cent-exact rounding - removing the currency-mismatch friction that blocks international buyers.
- Guaranteed exactly-once fulfilment on every payment: the verify-vs-webhook race is resolved by a unique index and an E11000 guard, so no customer is ever charged without access and no purchase is ever fulfilled twice.
- Kept checkout available through third-party outages: FX rates degrade from a TTL cache to the last good rates to safe defaults, with admin-pinned overrides - a rates provider going down never stops a sale.
- Eliminated double-booked mentor sessions and stale bookings: a UTC slot model rejects past slots for every timezone, and a unique-index guard turns simultaneous bookings into one winner and one clean rejection.
- Turned learning into verifiable, shareable credentials across TRISHUL paths, the 150 Problem Sheet and FTM, with cryptographically random credential ids and idempotent issuance - and a TRISHUL Master certificate as the capstone.
- Prepared learners for the AI era, not just interviews: an AI Architect path inside TRISHUL and an in-product assistant on Claude and Gemini, grounded in the platform's own curriculum.