How to Test LLM APIs for Free: Benchmarking, Latency & Quality Checks

The fastest way to verify an API key and measure raw endpoint latency:

# Test Groq with timing metrics
curl -w "\nTime Total: %{time_total}s\n" \
  https://api.groq.com/openai/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $GROQ_API_KEY" \
  -d '{
    "model": "llama-3.3-70b-versatile",
    "messages": [{"role": "user", "content": "Respond with OK."}]
  }'

In conversational apps, TTFT determines perceived snappiness. You can benchmark TTFT with this lightweight Python evaluation script:

```python import time, os from groq import Groq

client = Groq(api_key=os.environ.get("GROQ_API_KEY"))

start_time = time.perf_counter() stream = client.chat.completions.create( model="llama-3.3-70b-versatile", messages=[{"role": "user", "content": "Count from 1 to 10."}], stream=True )

first_token_time = None tokens = 0

for chunk in stream: if first_token_time is None and chunk.choices[0].delta.content: first_token_time = time.perf_counter() - start_time tokens += 1

total_time = time.perf_counter() - start_time print(f"Time to First Token (TTFT): {first_token_time * 1000:.1f}ms") print(f"Total Tokens: {tokens} | Throughput: {tokens / total_time:.1f} tokens/sec") ```