The Problem I Set Out to Solve
Ever wanted to use AI tools like grammar checkers, content generators, or email writers without paying expensive monthly subscriptions? I've been there. After testing multiple AI services, I thought: "What if I could create free AI tools by leveraging cost-effective API providers?"
That's how Daily AI Collection was born—a completely free, open-source platform with 100+ AI-powered tools using OpenRouter's affordable AI models. No registration required, no credit cards, just pure functionality.
In this article, I'll show you:
- 🏗️ How I architected the platform for 15-20 concurrent users on 8GB RAM
- 🤖 Why OpenRouter's multi-model approach provides speed and cost-efficiency
- ⚡ How I achieved 0.5-4 second response times with strategic model selection
- 💻 Complete tech stack breakdown with code examples
Ready to learn how to build free AI tools? Let's dive in!
🔗 Try it live: dailyaicollection.net
What I Built
Daily AI Collection is a free, open-source platform that provides 100+ AI-powered writing and productivity tools, including:
- ✍️ Grammar & Writing Tools: Grammar checker, paraphraser, text summarizer
- 📧 Business Tools: Email generator, resume builder, cover letter writer
- 📱 Content Creation: Social media captions, blog post generator, SEO optimizer
- 🎯 Personal Tools: Meeting notes summarizer, translation, text-to-speech
Key Features
✅ Completely Free - No subscriptions, no credits, no limits
✅ No Registration - Start using tools immediately
✅ 100+ Tools - Grammar, content, business, and personal tools
✅ Fast Processing - 2-4 second response times
✅ Privacy-Focused - No data storage or tracking
✅ Open Source - Fork, modify, self-host
Performance Metrics
- Response Time: 0.5-4 seconds (depending on model and task complexity)
- Concurrent Users: 15-20 simultaneous users on 8GB RAM
- Queue Processing: Efficient job management with Bull + Redis
- Uptime: 99.5% with automatic PM2 restart
- Cost: ~$0.01-0.05 per 1000 requests (vs $1-2 for premium APIs)
Table of Contents
- Tech Stack Decisions
- Architecture Breakdown
- Queue System Deep Dive
- Key Features Implementation
- Challenges and Solutions
- Performance Optimization
- Lessons Learned
- What's Next
Tech Stack Decisions
When building this platform, I had to make careful choices due to resource constraints (8GB RAM, 2 CPU cores). Here's what I chose and why:
Frontend: Next.js 14 + TypeScript
Why Next.js?
- ✅ Server-side rendering for fast initial loads
- ✅ API routes for backend integration
- ✅ Static generation for tool pages (instant loading)
- ✅ Image optimization built-in
- ✅ TypeScript for type safety
// Example: Tool page with SSG
export async function generateStaticParams() {
return tools.map((tool) => ({
id: tool.id,
}))
}
export default async function ToolPage({ params }: { params: { id: string } }) {
const tool = await getToolById(params.id)
return <ToolInterface tool={tool} />
}
Deployment: Vercel with automatic deployments
Backend: Node.js + Express
Why Node.js?
- ✅ Single language across stack (JavaScript/TypeScript)
- ✅ Excellent async handling for queue operations
- ✅ Fast I/O for API requests
- ✅ Bull + Redis integration for job queuing
// Express API structure
const express = require('express')
const app = express()
app.post('/api/process', async (req, res) => {
const { tool, text } = req.body
// Add to queue instead of processing directly
const job = await aiQueue.add({ tool, text })
res.json({
jobId: job.id,
estimatedTime: getEstimatedTime(tool)
})
})
app.get('/api/result/:jobId', async (req, res) => {
const job = await aiQueue.getJob(req.params.jobId)
const result = await job.finished()
res.json({ result })
})
Deployment: VPS with PM2 process manager
AI Engine: OpenRouter (Multi-Model API Gateway)
Why OpenRouter instead of direct OpenAI/Anthropic APIs?
Feature | OpenRouter | OpenAI Direct | Self-hosted (Ollama) |
---|---|---|---|
Cost | $0.01-0.05 per 1000 requests | $0.50-2.00 per 1000 requests | $0 (but slow) |
Speed | 0.5-4 seconds | 1-3 seconds | 5-15 seconds |
Model Choice | 100+ models | OpenAI only | Limited to what fits in RAM |
Privacy | Encrypted transit | Encrypted transit | 100% local |
Reliability | Auto-failover | Single provider | Server-dependent |
Setup | Just API key | API key | Complex setup |
Math: With 10,000 monthly requests:
- OpenRouter: $0.10-0.50/month = $1.20-6/year 💰
- OpenAI Direct: $5-20/month = $60-240/year
- Self-hosted: $0/month but slow response times
Model Selection Strategy:
const MODELS = {
// Fast grammar checking - Gemini Flash (fastest)
RESEARCH: 'google/gemini-2.0-flash-001',
// High-quality content - DeepSeek Chat (cost-effective)
WRITING: 'deepseek/deepseek-chat',
// Grammar refinement - Claude Haiku (accurate)
REFINEMENT: 'anthropic/claude-3.5-haiku',
// Reasoning tasks - DeepSeek R1 (advanced logic)
FACT_CHECK: 'deepseek/deepseek-r1'
}
function selectModel(tool) {
if (tool.category === 'grammar') return MODELS.REFINEMENT
if (tool.complexity === 'advanced') return MODELS.FACT_CHECK
if (tool.type === 'research') return MODELS.RESEARCH
return MODELS.WRITING
}
Pro Tip: OpenRouter lets you use premium models (Claude, GPT-4, Gemini) at 50-90% lower cost with automatic fallbacks!
Database: Supabase (PostgreSQL)
Why Supabase?
- ✅ Free tier: 500MB database, 1GB file storage
- ✅ PostgreSQL: Powerful relational database
- ✅ Built-in auth: User management (optional feature)
- ✅ Real-time: WebSocket subscriptions
- ✅ RLS policies: Row-level security
-- Example: Tool usage tracking
CREATE TABLE tool_usage (
id BIGSERIAL PRIMARY KEY,
tool_id VARCHAR(255) NOT NULL,
processing_time INTEGER,
model_used VARCHAR(50),
success BOOLEAN DEFAULT true,
created_at TIMESTAMP DEFAULT NOW()
);
-- Query: Most popular tools
SELECT tool_id, COUNT(*) as usage_count
FROM tool_usage
WHERE created_at > NOW() - INTERVAL '7 days'
GROUP BY tool_id
ORDER BY usage_count DESC
LIMIT 10;
Queue System: Bull + Redis
Why a queue system?
Without a queue, multiple users requesting AI processing simultaneously would crash the server. Here's the difference:
❌ Before (Direct Processing):
// User 1, 2, 3, 4, 5 all hit the API at once
app.post('/api/process', async (req, res) => {
const result = await openRouterAPI.generate(req.body.text)
// All requests processed simultaneously - rate limits exceeded
})
✅ After (Queue-Based):
// All users added to queue, processed fairly
app.post('/api/process', async (req, res) => {
const job = await aiQueue.add(req.body)
// Returns immediately, processes in background
res.json({ jobId: job.id })
})
Benefits:
- ⚡ Handles 15-20 concurrent users
- 🎯 Fair processing (FIFO queue)
- 💪 No server crashes
- 📊 Job status tracking
Architecture Breakdown
Here's how all the pieces fit together:
┌─────────────────────────────────────────────────────────┐
│ USER BROWSER │
│ (Next.js Frontend - Vercel) │
└─────────────────┬───────────────────────────────────────┘
│
│ 1. User submits text
│
▼
┌─────────────────────────────────────────────────────────┐
│ EXPRESS API SERVER │
│ (Node.js + Express - VPS) │
│ │
│ ┌──────────────────────────────────────────────────┐ │
│ │ POST /api/process │ │
│ │ - Validate input │ │
│ │ - Add job to queue │ │
│ │ - Return job ID │ │
│ └──────────────────────────────────────────────────┘ │
└─────────────────┬───────────────────────────────────────┘
│
│ 2. Job added to queue
│
▼
┌─────────────────────────────────────────────────────────┐
│ BULL + REDIS QUEUE │
│ (Job Management) │
│ │
│ Queue Stats: │
│ - Max 3 concurrent jobs │
│ - FIFO processing │
│ - Retry on failure (3 attempts) │
└─────────────────┬───────────────────────────────────────┘
│
│ 3. Job processed
│
▼
┌─────────────────────────────────────────────────────────┐
│ OPENROUTER AI GATEWAY │
│ (Multi-Model API Service) │
│ │
│ Models: │
│ - Gemini 2.0 Flash - Fast research │
│ - DeepSeek Chat - Content writing │
│ - Claude 3.5 Haiku - Grammar refinement │
│ - DeepSeek R1 - Advanced reasoning │
└─────────────────┬───────────────────────────────────────┘
│
│ 4. Result returned
│
▼
┌─────────────────────────────────────────────────────────┐
│ USER BROWSER │
│ (Displays processed result) │
└─────────────────────────────────────────────────────────┘
Request Flow Step-by-Step
- User Input: User enters text in frontend form
-
API Request: Frontend sends POST to
/api/process
- Queue Addition: Job added to Bull queue with priority
-
Position Update: Frontend polls
/api/status/:jobId
for queue position - Processing: OpenRouter processes job via selected model
- Result Storage: Result saved to Redis with 1-hour TTL
-
Result Retrieval: Frontend fetches result from
/api/result/:jobId
- Display: Processed text shown to user
Queue System Deep Dive
The queue system is the heart of this platform. Here's how I implemented it:
Queue Configuration
const Queue = require('bull')
const Redis = require('ioredis')
// Redis connection (used by Bull)
const redisClient = new Redis({
host: process.env.REDIS_HOST || 'localhost',
port: process.env.REDIS_PORT || 6379,
maxRetriesPerRequest: null
})
// AI Processing Queue
const aiQueue = new Queue('ai-processing', {
redis: {
host: process.env.REDIS_HOST,
port: process.env.REDIS_PORT
},
defaultJobOptions: {
attempts: 3, // Retry failed jobs 3 times
backoff: {
type: 'exponential', // Wait longer between retries
delay: 2000 // Start with 2 second delay
},
removeOnComplete: 100, // Keep last 100 completed jobs
removeOnFail: 500 // Keep last 500 failed jobs
},
limiter: {
max: 3, // Max 3 concurrent jobs
duration: 1000 // Per second
}
})
Job Processing Logic
// Process jobs from the queue
aiQueue.process(3, async (job) => {
const { tool, text, model } = job.data
// Update job progress
await job.progress(10)
// Select appropriate model
const selectedModel = model || selectModel(tool)
await job.progress(20)
try {
// Call OpenRouter with timeout
const result = await Promise.race([
axios.post('https://openrouter.ai/api/v1/chat/completions', {
model: selectedModel,
messages: buildMessages(tool, text),
temperature: 0.7,
max_tokens: 4000
}, {
headers: {
'Authorization': `Bearer ${process.env.OPENROUTER_API_KEY}`,
'HTTP-Referer': 'https://dailyaicollection.net',
'X-Title': 'Daily AI Collection'
}
}),
new Promise((_, reject) =>
setTimeout(() => reject(new Error('Timeout')), 30000)
)
])
await job.progress(90)
// Save to database
await trackUsage({
tool_id: tool,
model_used: selectedModel,
processing_time: job.finishedOn - job.processedOn,
success: true
})
await job.progress(100)
return {
result: result.response,
model: selectedModel,
processingTime: job.finishedOn - job.processedOn
}
} catch (error) {
// Log error and throw for retry mechanism
console.error(`Job ${job.id} failed:`, error)
throw error
}
})
// Event listeners for monitoring
aiQueue.on('completed', (job, result) => {
console.log(`✅ Job ${job.id} completed in ${job.finishedOn - job.processedOn}ms`)
})
aiQueue.on('failed', (job, err) => {
console.error(`❌ Job ${job.id} failed: ${err.message}`)
})
aiQueue.on('stalled', (job) => {
console.warn(`⚠️ Job ${job.id} stalled`)
})
Queue Dashboard
Monitor queue health in real-time:
// GET /api/queue/stats
app.get('/api/queue/stats', async (req, res) => {
const stats = {
waiting: await aiQueue.getWaitingCount(),
active: await aiQueue.getActiveCount(),
completed: await aiQueue.getCompletedCount(),
failed: await aiQueue.getFailedCount(),
delayed: await aiQueue.getDelayedCount()
}
res.json(stats)
})
Result: This queue system transformed server stability from constant crashes to 99.5% uptime with 15-20 concurrent users!
Key Features Implementation
Let me show you how I implemented some popular tools:
1. Grammar Checker (Gemini Flash via OpenRouter)
Why Gemini Flash? Google's Gemini 2.5 Flash is optimized for speed and accuracy at a fraction of the cost ($0.15/$0.60 per million tokens vs GPT-4's $30/$60).
async function checkGrammar(text) {
const prompt = `You are a professional grammar checker. Analyze this text and fix all grammar, spelling, and punctuation errors. Return only the corrected text without explanations.
Text to check: "${text}"
Corrected text:`
const response = await axios.post('https://openrouter.ai/api/v1/chat/completions', {
model: 'google/gemini-2.5-flash',
messages: [
{ role: 'system', content: 'You are a helpful AI assistant.' },
{ role: 'user', content: prompt }
],
temperature: 0.3,
max_tokens: 2000
}, {
headers: {
'Authorization': `Bearer ${process.env.OPENROUTER_API_KEY}`,
'HTTP-Referer': 'https://dailyaicollection.net',
'X-Title': 'Daily AI Collection'
}
})
return {
original: text,
corrected: response.data.choices[0].message.content,
model: 'google/gemini-2.5-flash',
usage: response.data.usage,
cost: calculateCost(response.data.usage) // ~$0.0001 per request
}
}
Performance: 0.5-2 seconds average response time ⚡
2. Email Generator (DeepSeek Chat via OpenRouter)
Why DeepSeek Chat? Excellent quality-to-cost ratio ($0.23/$0.90 per million tokens) with strong performance for business content generation.
async function generateEmail(purpose, tone, recipient, keyPoints) {
const prompt = `Generate a professional ${tone} email for the following purpose:
Purpose: ${purpose}
Recipient: ${recipient}
Key points to include:
${keyPoints.map((point, i) => `${i + 1}. ${point}`).join('\n')}
Write a complete email with subject line, greeting, body, and closing.`
const response = await axios.post('https://openrouter.ai/api/v1/chat/completions', {
model: 'deepseek/deepseek-chat-v3.1',
messages: [
{ role: 'system', content: 'You are a professional business communication assistant.' },
{ role: 'user', content: prompt }
],
temperature: 0.7,
max_tokens: 2000
}, {
headers: {
'Authorization': `Bearer ${process.env.OPENROUTER_API_KEY}`,
'HTTP-Referer': 'https://dailyaicollection.net',
'X-Title': 'Daily AI Collection'
}
})
const content = response.data.choices[0].message.content
// Parse email components
const lines = content.split('\n')
const subjectLine = lines.find(l => l.startsWith('Subject:'))
const body = lines.slice(lines.indexOf(subjectLine) + 1).join('\n')
return {
subject: subjectLine?.replace('Subject:', '').trim(),
body: body.trim(),
model: 'deepseek/deepseek-chat-v3.1',
usage: response.data.usage,
cost: calculateCost(response.data.usage) // ~$0.0002 per email
}
}
Performance: 1-3 seconds for 200-300 word emails ✉️
3. Text Summarizer (DeepSeek Chat via OpenRouter)
Why DeepSeek Chat? Excellent at understanding context and extracting key information while maintaining cost-efficiency.
async function summarizeText(text, maxLength = 150) {
const prompt = `Summarize the following text in ${maxLength} words or less. Focus on the main ideas and key takeaways.
Text:
${text}
Summary:`
const response = await axios.post('https://openrouter.ai/api/v1/chat/completions', {
model: 'deepseek/deepseek-chat-v3.1',
messages: [
{ role: 'system', content: 'You are an expert at summarizing text concisely.' },
{ role: 'user', content: prompt }
],
temperature: 0.5,
max_tokens: 2000
}, {
headers: {
'Authorization': `Bearer ${process.env.OPENROUTER_API_KEY}`,
'HTTP-Referer': 'https://dailyaicollection.net',
'X-Title': 'Daily AI Collection'
}
})
const summary = response.data.choices[0].message.content
return {
original: text,
summary,
wordCount: summary.split(' ').length,
compressionRatio: (summary.length / text.length * 100).toFixed(1),
model: 'deepseek/deepseek-chat-v3.1',
usage: response.data.usage,
cost: calculateCost(response.data.usage) // ~$0.0003 per summary
}
}
Performance: 1-4 seconds for 1000-word documents 📄
Challenges and Solutions
Building this platform wasn't without obstacles. Here's what I faced:
Challenge 1: Choosing Between Self-Hosted vs API-Based AI
Problem: Should I use self-hosted models (Ollama) or API-based providers (OpenRouter/OpenAI)?
Comparison:
- ❌ Self-Hosted (Ollama): Free but slow (5-15s), high RAM usage, limited to 8GB server
- ❌ OpenAI Direct: Fast but expensive ($30-60 per million tokens)
- ❌ Anthropic Direct: High quality but premium pricing ($15-75 per million tokens)
✅ Final Solution: OpenRouter multi-model API gateway for 50-90% cost savings with premium model access.
Benefits:
- No RAM constraints: API-based, no local model storage
- Cost-effective: $0.15-4.00 per million tokens (vs OpenAI's $30-60)
- Speed: 0.5-4 second response times (vs 5-15s for self-hosted)
- Flexibility: Access to 100+ models (Gemini, DeepSeek, Claude, GPT-4)
- Automatic fallback: If one model fails, OpenRouter tries alternatives
// OpenRouter Model Strategy (Cost-Optimized)
const MODEL_STRATEGY = {
'grammar': 'google/gemini-2.5-flash', // $0.15/$0.60 - Fast & cheap
'content': 'deepseek/deepseek-chat-v3.1', // $0.23/$0.90 - Balanced
'analysis': 'deepseek/deepseek-r1', // $0.01/$0.05 - Ultra-cheap reasoning
'creative': 'anthropic/claude-haiku-3.5', // $0.80/$4.00 - Premium quality
'technical': 'deepseek/deepseek-coder-v2' // $0.27/$1.10 - Code-optimized
}
// Estimated costs (10,000 requests/month):
// OpenRouter: $10-50/month ✅
// OpenAI Direct: $300-600/month ❌
// Savings: 80-95% 🎉
Challenge 2: Slow Response Times
Problem: How to optimize API response times and minimize costs?
Optimization Goals:
- Fast response times (< 4 seconds)
- Minimize API costs
- High cache hit rates for common requests
✅ Solutions Implemented:
1. Smart Model Selection:
// Tool-to-model mapping for optimal cost/performance
function selectOptimalModel(toolName) {
const modelStrategy = {
// Fast & cheap for grammar
'grammar': 'google/gemini-2.5-flash',
// Balanced for content
'content': 'deepseek/deepseek-chat-v3.1',
// Ultra-cheap for analysis
'analysis': 'deepseek/deepseek-r1',
// Premium for creative
'creative': 'anthropic/claude-haiku-3.5'
}
// Categorize tool
if (toolName.includes('grammar') || toolName.includes('spelling')) {
return modelStrategy.grammar
} else if (toolName.includes('poem') || toolName.includes('story')) {
return modelStrategy.creative
} else if (toolName.includes('analyz')) {
return modelStrategy.analysis
}
return modelStrategy.content // Default
}
2. Result Caching:
const cache = new Map()
async function getCachedResult(tool, text) {
const key = `${tool}:${hash(text)}`
// Check cache first
if (cache.has(key)) {
return { ...cache.get(key), cached: true }
}
// Process and cache
const result = await processText(tool, text)
cache.set(key, result)
// Auto-expire after 1 hour
setTimeout(() => cache.delete(key), 3600000)
return result
}
3. Optimized Prompts:
// ❌ Before: Verbose prompt (150 tokens)
const verbosePrompt = `
You are an advanced AI assistant specialized in grammar correction.
Your task is to carefully analyze the provided text...
[100+ more words]
`
// ✅ After: Concise prompt (30 tokens)
const optimizedPrompt = `Fix grammar and spelling errors. Return only corrected text.
Text: "${text}"
Corrected:`
Results:
- Response time: 0.5-4 seconds (API-based, no cold starts) ⚡
- Cache hit rate: 35-40% for common requests
- Cost per request: $0.0001-0.0005 (95% cheaper than OpenAI direct)
- User satisfaction significantly improved
Challenge 3: Concurrent Request Handling
Problem: How to handle multiple API requests efficiently without overwhelming the server?
Challenges:
- Multiple users submitting requests simultaneously
- API rate limits and quotas
- Request timeout management
- Cost control with concurrent requests
✅ Solution: Bull Queue System (covered earlier)
Before vs After:
Metric | Before Queue | After Queue |
---|---|---|
Max concurrent users | 3-5 | 15-20 |
Crash frequency | Daily | Never |
Response time consistency | Variable | Consistent |
Server uptime | ~85% | 99.5% |
Performance Optimization
Here are additional optimizations that made a huge difference:
1. Database Query Optimization
Before:
-- Slow query (full table scan)
SELECT * FROM tool_usage
WHERE tool_id = 'grammar-checker'
ORDER BY created_at DESC;
After:
-- Fast query (indexed)
CREATE INDEX idx_tool_usage_tool_created
ON tool_usage(tool_id, created_at DESC);
SELECT tool_id, COUNT(*) as usage_count
FROM tool_usage
WHERE created_at > NOW() - INTERVAL '7 days'
GROUP BY tool_id
ORDER BY usage_count DESC;
Result: Query time reduced from 800ms → 25ms 🚀
2. Frontend Optimization
Code splitting for faster loading:
// Dynamic imports for tool components
const GrammarChecker = dynamic(() => import('@/components/tools/grammar-checker'))
const EmailGenerator = dynamic(() => import('@/components/tools/email-generator'))
// Only load when user navigates to tool page
export default function ToolPage({ params }: { params: { id: string } }) {
return <ToolComponents[params.id] />
}
Result: Initial bundle size reduced from 450KB → 180KB 📦
3. API Response Caching
// Cache responses for 5 minutes
app.get('/api/tools', cache(300), async (req, res) => {
const tools = await getToolsList()
res.json(tools)
})
// Cache popular tool pages for 1 hour
app.get('/api/tools/:id', cache(3600), async (req, res) => {
const tool = await getToolById(req.params.id)
res.json(tool)
})
Result: API response time improved from 200ms → 5ms for cached requests ⚡
Lessons Learned
After building and running this platform, here's what I learned:
1. API-Based AI is More Practical Than Self-Hosted
Initially, I considered self-hosting models to avoid API costs. Wrong! OpenRouter's API-based approach provides better speed (0.5-4s vs 5-15s), no server constraints, and 80-95% cost savings compared to OpenAI direct.
Key insight: Choose the right model for each task, not the most expensive one.
2. Queue Systems Are Essential for Resource Management
Without Bull + Redis, this platform wouldn't exist. The queue system transformed an unstable server into a reliable production service.
Key insight: Always use queues for resource-intensive operations.
3. Prompt Engineering Is Critical
I spent days optimizing prompts. Short, specific prompts with clear instructions work best.
Example transformation:
- Before: 150-token verbose prompt → slower, higher costs
- After: 30-token concise prompt → faster, 50% cost reduction
Key insight: Less is more in prompt engineering.
4. Caching Saves Resources
35-40% of requests are for common text patterns (e.g., "Check grammar for this email"). Caching these saves significant processing time.
Key insight: Implement caching for frequently requested operations.
Try It Yourself
Ready to use free AI tools without monthly subscriptions?
🚀 Get started: dailyaicollection.net
💬 Join discussion: Leave a comment below
❤️ Support the project: Share with others who might benefit
Discussion Time!
I'd love to hear your thoughts:
- Which tool would you use most? Grammar checker, email generator, summarizer?
- What tool should I add next? Code reviewer, presentation writer, recipe generator?
- Would you self-host this? Interested in running it on your own server?
- API access - would you use it? Thinking of adding RESTful API
Drop your answers in the comments! 👇
For developers: What would you do differently with this tech stack? How would you handle scaling beyond 20 concurrent users?
Connect With Me
I'm actively building and sharing the journey:
- 💼 LinkedIn: Allan Ninal
- 📝 Dev.to: Follow for more articles in this series
- ☕ Support the project: ko-fi.com/allanninal
Thanks for reading! If you found this helpful, please share it with fellow developers who might benefit from free AI tools. ❤️
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