Why does my OpenAI API (ChatGPT) return 429 ‘rate limit exceeded’ even for low traffic?

I’m integrating OpenAI’s GPT API using Node.js. My app runs fine for a while, but then randomly throws:

Error: 429 - You exceeded your current quota, please check your plan and billing details.

Even with very low traffic (1–2 requests/min).

Here’s my sample code:

import OpenAI from "openai";
const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });

async function ask(question) {
  const res = await client.chat.completions.create({
    model: "gpt-4o-mini",
    messages: [{ role: "user", content: question }]
  });
  console.log(res.choices[0].message.content);
}
ask("Hello, world!");

Questions:

1. What causes random 429 errors even under low usage?

2. Should I add retry logic or a delay between requests?

3. Is there a way to check my actual request usage via API?