Kronos

Live at usekronos.tech

An upskilling ecosystem for the software engineering grind — LeetCode practice, system design, and cloud fundamentals in one place, with your friends there to keep you sharp. Link your LeetCode account and Kronos picks up new solves within the minute, turning them into progress rings, streaks, and a leaderboard you'd rather not be sitting at the bottom of.

Features

Interview prep

• Roadmaps — Blind 75, NeetCode 150, NeetCode 250, or every problem
• Progress broken down by category and by difficulty
• Automatic LeetCode sync, plus a manual re-sync
• Solutions viewer with runtime, the submitted code, and an optimal-solution tag

Study modules

• System Design problems with a drag-and-drop design canvas
• GenAI system design — designing LLM and generative-AI systems piece by piece
• Main components reference — the reusable building blocks and when to reach for each
• Cloud engineering — AWS and Azure services side by side
• Networking curriculum — packets through VPCs, security groups, and the edge

Community

• Group leaderboard, scoped by roadmap, with a difficulty breakdown
• Daily streaks and a calendar, backfilled from LeetCode timestamps
• Recent activity feed across the group
• Friends — requests, accept/decline, side-by-side progress, and a friend's solutions

Account & admin

• Clerk OAuth sign-in behind an admin approval gate
• Username change requests
• Light and dark themes
• Admin tools — approve pending members, rename users, view analytics, rotate the LeetCode session cookie

Architecture

flowchart LR
    U["Browser<br/>React + Vite"]
    CK["Clerk<br/>OAuth + JWT"]
    LC["LeetCode<br/>GraphQL"]

    subgraph AWS
        direction TB
        CF["CloudFront + S3<br/>static build"]
        AG["API Gateway<br/>HTTP API"]
        API["api lambda"]
        SYNC["sync lambda"]
        ENR["enrich lambda"]
        EB["EventBridge<br/>schedules"]
        SSM["SSM<br/>Parameter Store"]
        DB[("RDS Postgres")]
    end

    U --> CF
    U --> CK
    U -->|JWT| AG
    AG --> API
    API --> DB

    EB -->|every 1 min| SYNC
    EB -->|every 5 min| ENR
    SYNC --> LC
    ENR --> LC
    SYNC --> DB
    ENR --> DB

    SSM -.->|secrets at runtime| API
    SSM -.-> SYNC
    SSM -.-> ENR

Loading

Three Go lambdas share one codebase. api serves the dashboard, sync polls for new solves, and enrich backfills solution detail. None of them hold secrets — their environment carries SSM parameter names, and each reads the values at runtime, so rotating a credential needs no redeploy.

Layer
Frontend	React 19 + TypeScript, Vite, Tailwind v4
Auth	Clerk (OAuth, with admin approval)
Backend	Go on AWS Lambda (provided.al2023, arm64)
Data	RDS Postgres via pgx
Infra	Terraform — API Gateway HTTP API, EventBridge, S3 + CloudFront
CI/CD	GitHub Actions, OIDC to AWS, secrets in SSM Parameter Store

Prerequisites

Tool	Version	Needed for
Node	20.19+ or 22.12+	frontend (CI runs Node 20)
Go	1.23	backend lambdas
Terraform	1.x	infrastructure, deploy only

Node 22.8 will not do. If npm run build prints You are using Node.js 22.8.0. Vite requires Node.js version 20.19+ or 22.12+, you're in the gap between the two supported ranges. The build still completes, but it's an unsupported combination — move to 22.12+ or drop back to 20.19+.

Run locally

The frontend runs standalone — with no API and no Clerk key it renders the dashboard on local fixtures, which is enough for most UI work.

npm install
npm run dev

To point it at a deployed backend, create .env.local (git-ignored):

Variable	Effect
VITE_API_URL	Base URL of the HTTP API. Unset → local fixtures.
VITE_CLERK_PUBLISHABLE_KEY	Clerk key. Unset → auth is skipped entirely.

For the Go side — sync engine, seed generation, live verification against a real LeetCode user — see backend/README.md.

Scripts

Command	Does
npm run dev	Vite dev server with HMR
npm run build	tsc -b then production build to dist/
npm run lint	ESLint
npm run preview	Serve the built dist/

API surface

One lambda behind API Gateway, routed by path prefix. Every request carries a Clerk JWT; unapproved members get 403 outside a small pre-approval allowlist, and /admin/* requires the admin flag.

/me/*           profile, progress, calendar, streak, sync, theme, username
/leaderboard    group ranking       /group/difficulty   /recent   /users
/friends/*      list, requests, accept, decline
/sd/*           system-design progress and activity
/admin/*        pending, approve, users, analytics, leetcode-session

How syncing works

An EventBridge rule polls due members once a minute. The accepted-submission count acts as a cheap delta guard — zero means back off, a small delta is captured whole, a burst is flagged for confirmation. A second rule enriches solutions (runtime, code, optimality) every five minutes using an authenticated session. Details and the delta table are in backend/README.md.

Deploy

Pushing to main builds the lambdas, applies Terraform, loads the schema, and publishes the frontend. AWS auth is keyless via GitHub OIDC. Full one-time setup — state bucket, Parameter Store entries, OIDC role, Clerk config — is in DEPLOY.md. The deploy run logs print the live site URL.

Links

Live site	https://usekronos.tech
Repository	https://github.com/sah-rohan/leetcode-dashboard

License

No LICENSE file is present, so the default applies: all rights reserved by the repository owners. Add one if you intend to make the project reusable.