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Data Sources & Caching

Documentation for external APIs, data flow, and caching strategies.

Table of Contents

Overview

Crypto Data Aggregator fetches data from 13+ free, public APIs:

┌─────────────────┐  ┌─────────────────┐  ┌─────────────────┐  ┌─────────────────┐
│   CoinGecko     │  │   DeFiLlama     │  │  Alternative.me │  │  CryptoCompare  │
│  (Market Data)  │  │  (DeFi TVL)     │  │ (Fear & Greed)  │  │ (OHLCV/Social)  │
└────────┬────────┘  └────────┬────────┘  └────────┬────────┘  └────────┬────────┘
         │                    │                    │                    │
┌────────┴────────┐  ┌────────┴────────┐  ┌────────┴────────┐  ┌────────┴────────┐
│  Blockchain.com │  │    Messari      │  │   CoinGlass     │  │   GoPlus Labs   │
│  (BTC On-chain) │  │   (Research)    │  │ (Funding/OI)    │  │ (Token Security)│
└────────┬────────┘  └────────┬────────┘  └────────┬────────┘  └────────┬────────┘
         │                    │                    │                    │
┌────────┴────────┐  ┌────────┴────────┐  ┌────────┴────────┐  ┌────────┴────────┐
│   Etherscan     │  │  Mempool.space  │  │  Blockstream    │  │     Binance     │
│  (Gas Oracle)   │  │   (Mempool)     │  │  (Esplora API)  │  │ (Exchange Data) │
└────────┬────────┘  └────────┬────────┘  └────────┬────────┘  └────────┬────────┘
         │                    │                    │                    │
         └────────────────────┴────────────────────┴────────────────────┘
                                         │
                            ┌────────────▼────────────┐
                            │    Memory Cache (TTL)   │
                            └────────────┬────────────┘
                                         │
                            ┌────────────▼────────────┐
                            │     API Routes (/api)   │
                            └────────────┬────────────┘
                                         │
                            ┌────────────▼────────────┐
                            │     SWR Client Cache    │
                            └────────────┬────────────┘
                                         │
                            ┌────────────▼────────────┐
                            │      React Components   │
                            └─────────────────────────┘

External APIs

CoinGecko

Base URL: https://api.coingecko.com/api/v3

Authentication: None required (free tier)

Rate Limits: ~50 requests/minute

Endpoints Used

Endpoint Purpose Cache TTL
GET /coins/markets Top coins with market data 60s
GET /coins/{id} Detailed coin information 120s
GET /coins/{id}/market_chart Historical price data 300s
GET /coins/{id}/ohlc OHLC candlestick data 300s
GET /search/trending Trending coins 300s
GET /coins/categories/list Category list 3600s
GET /coins/categories Categories with market data 600s
GET /exchanges Exchange list 600s
GET /exchanges/{id} Exchange details 600s
GET /search Search coins 60s

Example Responses

GET /coins/markets

[
  {
    "id": "bitcoin",
    "symbol": "btc",
    "name": "Bitcoin",
    "image": "https://assets.coingecko.com/coins/images/1/large/bitcoin.png",
    "current_price": 95000,
    "market_cap": 1870000000000,
    "market_cap_rank": 1,
    "fully_diluted_valuation": 1990000000000,
    "total_volume": 45000000000,
    "high_24h": 96500,
    "low_24h": 93200,
    "price_change_24h": 1500,
    "price_change_percentage_24h": 1.6,
    "price_change_percentage_7d_in_currency": 5.2,
    "price_change_percentage_30d_in_currency": 12.5,
    "circulating_supply": 19600000,
    "total_supply": 21000000,
    "max_supply": 21000000,
    "ath": 100000,
    "ath_change_percentage": -5,
    "ath_date": "2025-01-15T00:00:00.000Z",
    "atl": 67.81,
    "atl_change_percentage": 139900,
    "atl_date": "2013-07-06T00:00:00.000Z",
    "last_updated": "2026-01-22T10:00:00.000Z",
    "sparkline_in_7d": {
      "price": [91000, 92500, 93000, ...]
    }
  }
]

GET /coins/{id}

{
  "id": "bitcoin",
  "symbol": "btc",
  "name": "Bitcoin",
  "description": {
    "en": "Bitcoin is the first successful..."
  },
  "links": {
    "homepage": ["https://bitcoin.org"],
    "blockchain_site": ["https://blockchair.com/bitcoin"],
    "repos_url": {
      "github": ["https://github.com/bitcoin/bitcoin"]
    }
  },
  "market_data": {
    "current_price": { "usd": 95000 },
    "market_cap": { "usd": 1870000000000 },
    "total_volume": { "usd": 45000000000 }
  },
  "community_data": {
    "twitter_followers": 6500000,
    "reddit_subscribers": 5000000
  },
  "developer_data": {
    "stars": 75000,
    "forks": 35000,
    "subscribers": 4000
  }
}

DeFiLlama

Base URL: https://api.llama.fi

Authentication: None required

Rate Limits: Very generous (no documented limits)

Endpoints Used

Endpoint Purpose Cache TTL
GET /protocols All DeFi protocols 300s
GET /chains All chains with TVL 300s
GET /protocol/{name} Protocol details & history 300s
GET /tvl/{protocol} Protocol TVL 300s

Example Responses

GET /protocols

[
  {
    "id": "1",
    "name": "Lido",
    "symbol": "LDO",
    "url": "https://lido.fi",
    "description": "Liquid staking for Ethereum",
    "chain": "Multi-Chain",
    "logo": "https://defillama.com/icons/lido.png",
    "tvl": 35000000000,
    "chainTvls": {
      "Ethereum": 32000000000,
      "Polygon": 500000000,
      "Solana": 2500000000
    },
    "change_1h": 0.1,
    "change_1d": 1.5,
    "change_7d": 3.2,
    "category": "Liquid Staking"
  }
]

Alternative.me

Base URL: https://api.alternative.me

Authentication: None required

Rate Limits: Unknown (generous)

Endpoints Used

Endpoint Purpose Cache TTL
GET /fng/ Current Fear & Greed Index 3600s
GET /fng/?limit=30 Historical Fear & Greed 3600s

Example Response

GET /fng/

{
  "name": "Fear and Greed Index",
  "data": [
    {
      "value": "72",
      "value_classification": "Greed",
      "timestamp": "1737504000",
      "time_until_update": "43200"
    }
  ],
  "metadata": {
    "error": null
  }
}

CryptoCompare

Base URL: https://min-api.cryptocompare.com/data

Authentication: None required for basic tier

Rate Limits: 100,000 calls/month (free tier)

Endpoints Used

Endpoint Purpose Cache TTL
GET /histoday Daily OHLCV data 300s
GET /histohour Hourly OHLCV data 300s
GET /histominute Minute OHLCV data 60s
GET /social/coin/latest Social stats (Twitter, Reddit, GitHub) 3600s

Example Response

GET /histoday?fsym=BTC&tsym=USD&limit=7

{
  "Response": "Success",
  "Data": [
    {
      "time": 1737417600,
      "open": 94500,
      "high": 96200,
      "low": 93800,
      "close": 95800,
      "volumefrom": 12500,
      "volumeto": 1187500000
    }
  ]
}

Blockchain.com

Base URL: https://api.blockchain.info

Authentication: None required

Rate Limits: Unlimited

Endpoints Used

Endpoint Purpose Cache TTL
GET /stats Bitcoin network statistics 600s
GET /q/getblockcount Current block height 60s

Example Response

GET /stats?format=json

{
  "market_price_usd": 95800,
  "hash_rate": 750000000000000000000,
  "difficulty": 110568893081062,
  "totalbc": 1960000000000000,
  "n_tx": 450000,
  "minutes_between_blocks": 9.5,
  "total_fees_btc": 2500000000
}

Messari

Base URL: https://data.messari.io/api/v1

Authentication: None required for public endpoints

Rate Limits: 20 requests/minute (free tier)

Endpoints Used

Endpoint Purpose Cache TTL
GET /assets List all assets 600s
GET /assets/{symbol}/metrics Asset metrics & research 300s

Example Response

GET /assets/btc/metrics

{
  "data": {
    "id": "1e31218a-e44e-4285-820c-8282ee222035",
    "symbol": "BTC",
    "name": "Bitcoin",
    "slug": "bitcoin",
    "market_data": {
      "price_usd": 95800,
      "volume_last_24_hours": 45000000000,
      "percent_change_usd_last_24_hours": 1.5
    },
    "marketcap": {
      "current_marketcap_usd": 1876000000000
    },
    "roi_data": {
      "percent_change_last_1_week": 5.2
    }
  }
}

CoinGlass

Base URL: https://open-api.coinglass.com/public/v2

Authentication: None required for public endpoints

Rate Limits: Generous (undocumented)

Endpoints Used

Endpoint Purpose Cache TTL
GET /funding Funding rates by exchange 300s
GET /open_interest Open interest aggregated 300s

Example Response

GET /funding?symbol=BTC

{
  "code": "0",
  "data": [
    {
      "symbol": "BTC",
      "exchangeName": "Binance",
      "rate": 0.0001,
      "predictedRate": 0.00012,
      "nextFundingTime": 1737504000000
    },
    {
      "symbol": "BTC",
      "exchangeName": "Bybit",
      "rate": 0.00008,
      "predictedRate": 0.0001,
      "nextFundingTime": 1737504000000
    }
  ]
}

GoPlus Labs

Base URL: https://api.gopluslabs.io/api/v1

Authentication: None required

Rate Limits: Unlimited

Endpoints Used

Endpoint Purpose Cache TTL
GET /token_security/{chainId} Token security analysis 3600s

Chain IDs

Chain ID
Ethereum 1
BSC 56
Polygon 137
Arbitrum 42161
Base 8453

Example Response

GET /token_security/1?contract_addresses=0x....

{
  "code": 1,
  "result": {
    "0x....": {
      "is_open_source": "1",
      "is_proxy": "0",
      "is_mintable": "0",
      "is_honeypot": "0",
      "buy_tax": "0",
      "sell_tax": "0",
      "holder_count": "150000",
      "lp_holder_count": "25"
    }
  }
}

Etherscan

Base URL: https://api.etherscan.io/api

Authentication: None required for basic endpoints

Rate Limits: 5 calls/second (free tier)

Endpoints Used

Endpoint Purpose Cache TTL
GET ?module=gastracker&action=gasoracle Current gas prices 15s
GET ?module=stats&action=ethsupply2 ETH supply stats 3600s

Example Response

GET ?module=gastracker&action=gasoracle

{
  "status": "1",
  "result": {
    "LastBlock": "19500000",
    "SafeGasPrice": "15",
    "ProposeGasPrice": "18",
    "FastGasPrice": "22",
    "suggestBaseFee": "14.5",
    "gasUsedRatio": "0.45,0.52,0.48,0.55,0.50"
  }
}

Mempool.space

Base URL: https://mempool.space/api

Authentication: None required

Rate Limits: Generous

Endpoints Used

Endpoint Purpose Cache TTL
GET /v1/fees/recommended Recommended BTC fees 60s
GET /blocks/tip/height Current block height 60s
GET /mempool Mempool statistics 30s

Blockstream

Base URL: https://blockstream.info/api

Authentication: None required

Rate Limits: Generous

Endpoints Used

Endpoint Purpose Cache TTL
GET /blocks/tip/height Current block height 60s
GET /block/{hash} Block details 3600s
GET /tx/{txid} Transaction details 3600s

Caching Strategy

Multi-Layer Cache

┌──────────────────────────────────────────────────┐
│  Layer 1: SWR Client Cache (Browser)             │
│  - Stale-while-revalidate pattern                │
│  - Automatic revalidation on focus               │
│  - Deduplication of concurrent requests          │
├──────────────────────────────────────────────────┤
│  Layer 2: Memory Cache (Edge/Server)             │
│  - TTL-based expiration                          │
│  - LRU eviction when memory limit reached        │
│  - Shared across API route invocations           │
├──────────────────────────────────────────────────┤
│  Layer 3: HTTP Cache Headers                     │
│  - Cache-Control headers                         │
│  - ETag for conditional requests                 │
│  - CDN/browser caching                           │
└──────────────────────────────────────────────────┘

Cache Implementation

Location: src/lib/cache.ts

interface CacheEntry<T> {
  data: T;
  timestamp: number;
  ttl: number;
}

class MemoryCache {
  private cache: Map<string, CacheEntry<unknown>> = new Map();
  private maxSize: number = 100;

  get<T>(key: string): T | null {
    const entry = this.cache.get(key);
    if (!entry) return null;

    if (Date.now() - entry.timestamp > entry.ttl * 1000) {
      this.cache.delete(key);
      return null;
    }

    return entry.data as T;
  }

  set<T>(key: string, data: T, ttl: number): void {
    // LRU eviction if at capacity
    if (this.cache.size >= this.maxSize) {
      const oldestKey = this.cache.keys().next().value;
      this.cache.delete(oldestKey);
    }

    this.cache.set(key, {
      data,
      timestamp: Date.now(),
      ttl,
    });
  }
}

export const cache = new MemoryCache();

Cache TTL by Data Type

Data Type TTL Reason
Coin prices 60s Balance freshness vs. API limits
Coin details 120s Less volatile data
Historical charts 300s Historical data doesn't change
Trending 300s Updates hourly on source
Categories list 3600s Rarely changes
DeFi protocols 300s TVL updates frequently
Fear & Greed 3600s Updates daily

SWR Configuration

// Global SWR config
<SWRConfig
  value={{
    fetcher: (url) => fetch(url).then((r) => r.json()),
    revalidateOnFocus: true,
    revalidateOnReconnect: true,
    dedupingInterval: 5000,
    errorRetryCount: 3,
  }}
>
  <App />
</SWRConfig>

// Per-hook config
const { data } = useSWR('/api/market/coins', fetcher, {
  refreshInterval: 30000,  // Refresh every 30s
  revalidateIfStale: true,
  revalidateOnMount: true,
});

Data Models

CoinData

interface CoinData {
  id: string;
  symbol: string;
  name: string;
  image: string;
  current_price: number;
  market_cap: number;
  market_cap_rank: number;
  total_volume: number;
  high_24h: number;
  low_24h: number;
  price_change_24h: number;
  price_change_percentage_24h: number;
  price_change_percentage_7d_in_currency?: number;
  price_change_percentage_30d_in_currency?: number;
  circulating_supply: number;
  total_supply: number | null;
  max_supply: number | null;
  ath: number;
  ath_change_percentage: number;
  ath_date: string;
  last_updated: string;
  sparkline_in_7d?: {
    price: number[];
  };
}

DeFiProtocol

interface DeFiProtocol {
  id: string;
  name: string;
  symbol: string;
  url: string;
  description: string;
  chain: string;
  chains: string[];
  logo: string;
  tvl: number;
  change_1h: number;
  change_1d: number;
  change_7d: number;
  category: string;
  chainTvls: Record<string, number>;
}

PriceAlert

interface PriceAlert {
  id: string;
  coinId: string;
  coinName: string;
  coinSymbol: string;
  type: 'above' | 'below';
  targetPrice: number;
  currentPrice: number;
  enabled: boolean;
  triggered: boolean;
  createdAt: string;
  triggeredAt?: string;
}

PortfolioHolding

interface PortfolioHolding {
  coinId: string;
  symbol: string;
  name: string;
  amount: number;
  averagePrice: number;
  notes?: string;
  addedAt: string;
}

Error Handling

API Error Response

interface APIError {
  error: string;
  code: string;
  details?: unknown;
}

// Example error response
{
  "error": "Failed to fetch market data",
  "code": "UPSTREAM_ERROR",
  "details": {
    "status": 429,
    "message": "Rate limit exceeded"
  }
}

Error Handling Pattern

// In API route
export async function GET(request: Request) {
  try {
    const data = await fetchMarketData();
    return Response.json(data);
  } catch (error) {
    console.error('Market data fetch failed:', error);

    if (error instanceof RateLimitError) {
      return Response.json({ error: 'Rate limit exceeded', code: 'RATE_LIMIT' }, { status: 429 });
    }

    // Try to return cached data on error
    const cached = cache.get('market-data-fallback');
    if (cached) {
      return Response.json({
        ...cached,
        _stale: true,
        _cachedAt: cached._timestamp,
      });
    }

    return Response.json({ error: 'Service unavailable', code: 'SERVICE_ERROR' }, { status: 503 });
  }
}

Client-Side Error Handling

const { data, error, isLoading } = useSWR('/api/market/coins', fetcher, {
  onError: (err) => {
    console.error('Failed to fetch:', err);
    showToast({ type: 'error', message: 'Failed to load market data' });
  },
  errorRetryCount: 3,
  errorRetryInterval: 5000,
});

if (error) {
  return <ErrorState message="Unable to load data" onRetry={mutate} />;
}

Rate Limiting

Strategy

To stay within free tier limits, we:

  1. Cache aggressively - Reduce duplicate requests
  2. Batch requests - Combine multiple coin requests
  3. Debounce user actions - Prevent rapid-fire requests
  4. Fallback to cached data - Serve stale data on rate limit

Implementation

// Debounced search
const debouncedSearch = useMemo(
  () =>
    debounce((query: string) => {
      mutate(`/api/search?q=${query}`);
    }, 300),
  []
);

// Request batching for coin prices
async function getBatchedPrices(coinIds: string[]): Promise<PriceMap> {
  // CoinGecko allows up to 250 coins per request
  const batches = chunk(coinIds, 250);
  const results = await Promise.all(
    batches.map((batch) => fetch(`/api/market/coins?ids=${batch.join(',')}`))
  );
  return mergeResults(results);
}

Rate Limit Headers

API routes return rate limit headers:

X-RateLimit-Limit: 50
X-RateLimit-Remaining: 45
X-RateLimit-Reset: 1737550000

Data Freshness Indicators

Components can show data freshness:

interface DataWithMeta<T> {
  data: T;
  _cachedAt: number;
  _stale: boolean;
}

function PriceDisplay({ price, cachedAt, stale }: Props) {
  const age = Date.now() - cachedAt;

  return (
    <div>
      <span>${price}</span>
      {stale && <span className="text-yellow-500 text-xs">(cached {formatAge(age)} ago)</span>}
    </div>
  );
}

Additional Data Sources (For Future Integration)

1. CryptoCompare

Base URL: https://min-api.cryptocompare.com

Free tier includes 250,000 calls/month. Excellent for historical data.

Endpoint Description Rate Limit
/data/pricemultifull Multi-price with full data 50 req/sec
/data/v2/histoday Daily OHLCV history 50 req/sec
/data/v2/histohour Hourly OHLCV history 50 req/sec
/data/v2/histominute Minute OHLCV history 50 req/sec
/data/top/totalvolfull Top coins by volume 50 req/sec
/data/blockchain/histo/day On-chain metrics 50 req/sec 
# Example: Multi-price request
curl "https://min-api.cryptocompare.com/data/pricemultifull?fsyms=BTC,ETH&tsyms=USD"

Use Cases: Historical OHLCV data, social stats, on-chain metrics

2. Binance Public API

Base URL: https://api.binance.com

No authentication required for public endpoints. Very high rate limits.

Endpoint Description Rate Limit
/api/v3/ticker/24hr 24h price change stats 1200 req/min
/api/v3/klines Candlestick/OHLCV data 1200 req/min
/api/v3/depth Order book depth 1200 req/min
/api/v3/trades Recent trades 1200 req/min
/api/v3/avgPrice Current average price 1200 req/min
/fapi/v1/openInterest Futures open interest 500 req/min
/fapi/v1/fundingRate Funding rate history 500 req/min 
# Example: 24h ticker for BTCUSDT
curl "https://api.binance.com/api/v3/ticker/24hr?symbol=BTCUSDT"

# Example: Funding rates
curl "https://fapi.binance.com/fapi/v1/fundingRate?symbol=BTCUSDT&limit=10"

Use Cases: Real-time prices, order book data, funding rates, open interest

3. Etherscan API

Base URL: https://api.etherscan.io/api

Free tier: 5 calls/sec. Requires free API key.

Endpoint Description Rate Limit
?module=gastracker&action=gasoracle Gas price oracle 5 req/sec
?module=stats&action=ethprice ETH price 5 req/sec
?module=stats&action=ethsupply2 ETH total supply 5 req/sec
?module=account&action=balance Address balance 5 req/sec
?module=account&action=tokentx ERC-20 transfers 5 req/sec 
# Example: Gas oracle
curl "https://api.etherscan.io/api?module=gastracker&action=gasoracle&apikey=YOUR_KEY"

Use Cases: Gas tracking (already using Alternative.me), whale watching, token transfers

4. CoinMarketCap (Free Tier)

Base URL: https://pro-api.coinmarketcap.com

Free tier: 10,000 credits/month (~330/day). Requires API key.

Endpoint Description Credits
/v1/cryptocurrency/listings/latest Top coins listing 1
/v1/cryptocurrency/quotes/latest Price quotes 1 per coin
/v1/global-metrics/quotes/latest Global market stats 1
/v1/cryptocurrency/categories Category list 1
/v1/fear-and-greed/latest Fear & Greed index 1

Use Cases: Alternative market data source, category rankings

5. Messari API

Base URL: https://data.messari.io/api

Free tier: 20 requests/minute, no key required for basic endpoints.

Endpoint Description Rate Limit
/v1/assets All assets list 20 req/min
/v1/assets/{symbol}/profile Asset profile/fundamentals 20 req/min
/v1/assets/{symbol}/metrics Asset metrics 20 req/min
/v2/assets/{symbol}/timeseries/price Price timeseries 20 req/min
/v1/news News feed 20 req/min 
# Example: Bitcoin profile
curl "https://data.messari.io/api/v1/assets/btc/profile"

# Example: Market metrics
curl "https://data.messari.io/api/v1/assets/btc/metrics"

Use Cases: Fundamental data, project profiles, on-chain metrics, news

6. Blockchain.com API

Base URL: https://api.blockchain.info

No authentication required. Bitcoin-specific data.

Endpoint Description Rate Limit
/stats Bitcoin network stats Generous
/rawblock/{hash} Block data Generous
/rawtx/{hash} Transaction data Generous
/q/hashrate Network hashrate Generous
/q/getdifficulty Mining difficulty Generous
/q/24hrbtc BTC sent last 24h Generous 
# Example: Bitcoin stats
curl "https://api.blockchain.info/stats"

Use Cases: Bitcoin on-chain data, network health, mining stats

7. GlassNode (Limited Free)

Base URL: https://api.glassnode.com

Limited free tier with API key. Premium for full access.

Metric Category Examples
Addresses Active, new, with balance
Mining Hashrate, difficulty, revenue
Market MVRV, SOPR, NVT
Supply Circulating, liquid, illiquid

Use Cases: Advanced on-chain analytics (limited free data)

8. CoinPaprika API

Base URL: https://api.coinpaprika.com/v1

Free, no authentication required. 10 requests/second.

Endpoint Description Rate Limit
/coins All coins list 10 req/sec
/coins/{id} Coin details 10 req/sec
/coins/{id}/ohlcv/today Today's OHLCV 10 req/sec
/tickers All tickers 10 req/sec
/global Global market data 10 req/sec
/exchanges All exchanges 10 req/sec 
# Example: Global market data
curl "https://api.coinpaprika.com/v1/global"

# Example: Bitcoin ticker
curl "https://api.coinpaprika.com/v1/tickers/btc-bitcoin"

Use Cases: Alternative to CoinGecko, exchange data

9. Coinglass API

Base URL: https://open-api.coinglass.com/public/v2

Free public endpoints for derivatives data.

Endpoint Description
/open_interest Open interest across exchanges
/funding Funding rates
/liquidation_history Liquidation history
/long_short Long/short ratio 
# Example: Open interest
curl "https://open-api.coinglass.com/public/v2/open_interest?symbol=BTC"

Use Cases: Derivatives data, liquidations, funding rates, sentiment

10. NFT Data Sources

OpenSea API (Limited Free)

  • Base URL: https://api.opensea.io/api/v2
  • Requires API key, free tier available
  • Collection stats, floor prices, sales

NFTPort (Free Tier)

  • Base URL: https://api.nftport.xyz
  • 50 requests/day free
  • Multi-chain NFT data

Integration Priority Matrix

Source Priority Effort Value Add
Binance Public API 🔴 High Low Real-time prices, derivatives
CryptoCompare 🔴 High Medium Historical data, social
Messari 🟡 Medium Low Fundamentals, news
CoinPaprika 🟡 Medium Low Redundancy, exchange data
Coinglass 🟡 Medium Medium Derivatives analytics
Blockchain.com 🟢 Low Low BTC on-chain
Etherscan 🟢 Low Medium ETH on-chain
NFT Sources 🟢 Low High NFT markets

Recommended Integration Approach

  1. Start with Binance Public API - No auth, high limits, real-time data
  2. Add CryptoCompare - Fill historical data gaps
  3. Integrate Messari - Add fundamental data layer
  4. Add Coinglass - Enhance derivatives features
  5. Consider NFT sources - If expanding to NFT market data