Champanzee

URL: https://champanzee.tech GITHUB: https://github.com/rbous/champanzee

How We Built It

We designed and implemented Champanzee as a horizontally scalable, Kahoot-like survey platform where players progress asynchronously (not synchronized per question). Each participant advances at their own pace while still competing on a shared leaderboard.

At a high level, the system is built around Survey templates, Live Rooms, Per-player queues, and an AI-powered evaluation and follow-up engine.

Core Architecture

To support real-time interaction, AI evaluation, and scalability, we used a hybrid architecture:

Redis (Live State & Performance Layer)
Redis acts as the source of truth for all live data:
- Room state and status
- Player sessions and per-player question queues
- Leaderboards (using sorted sets)
- Draft answers, attempts, and follow-up pools

This allows constant-time updates without expensive database queries and makes horizontal scaling (multi-instance servers, Kubernetes) feasible.

MongoDB (Persistence Layer)
MongoDB stores long-lived data:
- Survey templates
- Full player responses
- AI evaluations and extracted signals
- Post-room analytics and reports

Its NoSQL structure fits our deeply nested and evolving data models (questions, analytics, AI outputs).

WebSockets (Real-Time Communication)
We used Go with the Gorilla WebSocket library for high concurrency and low latency.
Hosts receive real-time leaderboard and analytics updates, while players get instant feedback without polling.

Survey → Room → Player Flow

Host Flow

The host creates a Survey template (stored in MongoDB) containing base questions and scoring rules.
A Room is created from the survey:
- Live room state is initialized in Redis
- A room code is generated for players
The host uploads contextual material (slides or descriptions).
- AI summarizes this into a scope anchor stored in Redis.
AI generates follow-up question pools for each base question.
- The host can review and approve them.
The room status switches to ACTIVE, and the host receives live updates via WebSockets.

Player Flow (Async Pace)

A player joins using the room code and receives a session token.
Each player gets a personal question queue initialized as:

( Q = [Q_1, Q_2, Q_3, \dots] )

Draft answers are saved locally and optionally in Redis to avoid retyping.
When an answer is submitted:
- The response is stored
- AI evaluates the answer
- Scores, analytics, and leaderboards are updated
If needed, a follow-up question is inserted into the player’s queue.
The player continues until their queue is empty.

Question Types & AI Evaluation

We support multiple question types with different behaviors:

Essay Questions
- Free-text answers
- AI evaluates quality and determines if the answer is satisfactory
- Can gate progression
- Can trigger follow-ups
- Higher point value
Degree / Rating Questions
- Numeric answers (e.g. 1–5 or sliders)
- Never gate progression
- Can trigger follow-ups based on thresholds or outliers
- Strong input for analytics

For essay questions, AI extracts structured signals such as:

Themes
Missing details
Clarity and specificity
Sentiment
One-sentence summaries

These signals are used for both scoring and analytics.

Scoring & Leaderboards

All scoring is server-owned to prevent manipulation.

For essay questions, points are computed as:

$$ \text{points} = \min\left( \text{qualityScore} \times \text{pointsMax}, \ \text{pointsMax} \right) $$

Degree questions award fixed or scaled participation points.

Leaderboards are maintained in Redis using sorted sets, allowing instant ranking updates without costly re-sorting.

Follow-Up System

Follow-ups are a core feature of Champanzee and include:

AI-generated question pools (host-approved)
On-demand personalized probes
Clarification questions (missing details)
Deepening questions (examples, trade-offs)
Challenge questions (inconsistencies)
Comparison questions (forced choices)

If a player skips a question, all remaining follow-ups linked to that question are automatically closed, while drafts and previous answers are preserved.