How to handle exchange rate API errors and rate limits?

[cahthuranag]

What errors can the API return and how should I handle rate limiting in production?

Answer

Error codes:

Status	Meaning	What to do
400	Bad request (missing/invalid params)	Check your parameters
401	Invalid or missing API key	Verify your API key
404	Currency code not found	Check currency code spelling
429	Rate limit exceeded	Implement caching (see below)
500	Server error	Retry with exponential backoff

JavaScript error handling:

import { ExchangeRateAPI, ExchangeRateAPIError } from '@exchangerateapi/sdk';

const client = new ExchangeRateAPI({ apiKey: 'era_live_YOUR_KEY' });

try {
  const data = await client.latest();
} catch (err) {
  if (err instanceof ExchangeRateAPIError) {
    if (err.status === 429) {
      console.log('Rate limited, using cache');
    } else {
      console.error(`API error: ${err.message} (${err.status})`);
    }
  }
}

Python error handling:

from exchangerateapi import ExchangeRateAPI, ExchangeRateAPIError

client = ExchangeRateAPI(api_key="era_live_YOUR_KEY")

try:
    data = client.latest()
except ExchangeRateAPIError as e:
    print(f"Error: {e} (status: {e.status})")

Best practice: Cache rates

Exchange rates don't change every second. Cache responses for 60 seconds to minimize API calls:

let cache = { data: null, timestamp: 0 };

async function getRates() {
  const now = Date.now();
  if (cache.data && now - cache.timestamp < 60000) {
    return cache.data;
  }
  const data = await client.latest({ base: 'USD' });
  cache = { data, timestamp: now };
  return data;
}

This reduces your API usage dramatically while still serving fresh data.

[cahthuranag]

Error codes:

Status	Meaning	What to do
400	Bad request (missing/invalid params)	Check your parameters
401	Invalid or missing API key	Verify your API key
404	Currency code not found	Check currency code spelling
429	Rate limit exceeded	Implement caching (see below)
500	Server error	Retry with exponential backoff

JavaScript error handling:

import { ExchangeRateAPI, ExchangeRateAPIError } from '@exchangerateapi/sdk';

const client = new ExchangeRateAPI({ apiKey: 'era_live_YOUR_KEY' });

try {
  const data = await client.latest();
} catch (err) {
  if (err instanceof ExchangeRateAPIError) {
    if (err.status === 429) {
      console.log('Rate limited, using cache');
    } else {
      console.error(`API error: ${err.message} (${err.status})`);
    }
  }
}

Python error handling:

from exchangerateapi import ExchangeRateAPI, ExchangeRateAPIError

client = ExchangeRateAPI(api_key="era_live_YOUR_KEY")

try:
    data = client.latest()
except ExchangeRateAPIError as e:
    print(f"Error: {e} (status: {e.status})")

Best practice: Cache rates

Exchange rates don't change every second. Cache responses for 60 seconds to minimize API calls:

let cache = { data: null, timestamp: 0 };

async function getRates() {
  const now = Date.now();
  if (cache.data && now - cache.timestamp < 60000) {
    return cache.data;
  }
  const data = await client.latest({ base: 'USD' });
  cache = { data, timestamp: now };
  return data;
}

This reduces your API usage dramatically while still serving fresh data.