DeepSeek V4 Flash vs Gemini 3.1 Pro Preview
Pricing, context window and real answers (September 2026)
DeepSeek V4 Flash (DeepSeek) and Gemini 3.1 Pro Preview (Google), compared as you can actually call them on FastMetal. Both are served from the same OpenAI-compatible endpoint and API key; switching is a change to the model string.
Specs and pricing
 DeepSeek V4 Flash |  Gemini 3.1 Pro Preview | |
|---|---|---|
| Provider | DeepSeek | |
| Input (per 1M tokens) | ¥24.61 | ¥357.4 |
| Output (per 1M tokens) | ¥49.21 | ¥2,144.4 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥49 | ¥1,430 |
| Context window | 1,048,576 tokens | 1,048,576 tokens |
| Release date | 4/24/2026 | 2/19/2026 |
| Input modalities | text | audio, file, image, text, video |
| Throughput (p50) | — | — |
| Arena · overall | #92 · ELO 1,436 | #15 · ELO 1,487 |
| Arena · Japanese | #78 · ELO 1,396 | #9 · ELO 1,494 |
| Arena · coding | #92 · ELO 1,483 | #28 · ELO 1,520 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, DeepSeek V4 Flash: ¥49.21 per 1M output tokens, 98% less than Gemini 3.1 Pro Preview.
- On the Overall arena board, Gemini 3.1 Pro Preview ranks higher (#15; DeepSeek V4 Flash is #92).
- On the Japanese arena board, Gemini 3.1 Pro Preview ranks higher (#9; DeepSeek V4 Flash is #78).
- On the Coding arena board, Gemini 3.1 Pro Preview ranks higher (#28; DeepSeek V4 Flash is #92).
- If in doubt, try both on the same key. Switching is a change to the model string, and each is billed at its own rate.
Real answers to the same prompts
Exactly what the FastMetal gateway returned, side by side. Not benchmark scores: actual output.
Count the number of 'r's in 'strawberry'
Count the number of 'r's in 'strawberry'. Explain your reasoning step by step.
DeepSeek V4 Flash
The word "strawberry" is spelled as s-t-r-a-w-b-e-r-r-y. I go through each letter: s (no), t (no), r (yes, first), a (no), w (no), b (no), e (no), r (yes, second), r (yes, third), y (no). Thus, there are three 'r's.
3.9s251 output tokens
Gemini 3.1 Pro Preview
There are **3** 'r's in the word 'strawberry'.
Here is the step-by-step breakdown of the spelling:
1. **s** - not an 'r'
2. **t** - not an 'r'
3. **r** - **1st 'r'**
4. **a** - not an 'r'
5. **w** - not an 'r'
6. **b** - not an 'r'
7. **e** - not an 'r'
8. **r** - **2nd 'r'**
9. **r** - **3rd 'r'**
10. **y** - not an 'r'
Therefore, the total count is 3.
5.3s503 output tokens
Debug This Error
I'm getting the following error in my Node.js application: TypeError: Cannot read properties of undefined (reading 'map') at UserList (/app/components/UserList.js:12:25) at renderWithHooks (/app/node_modules/rea…
DeepSeek V4 Flash
The error occurs because `users` is `undefined` when the component tries to call `.map()` on it.
## Why this happens
Your component expects `users` to be an array, but it's receiving `undefined` as a prop. This typically happens when:
1. The parent component doesn't pass the `users` prop
2. The data fetching hasn't completed yet (async data loading)
3. The API response is missing the expected data structure
## How to fix it
### Option 1: Default prop value (Recommended for initial state)
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
### Option 2: Guard clause (More explicit)
```jsx
func…
6.3s422 output tokens
Gemini 3.1 Pro Preview
### The Cause
This error occurs because the `users` prop being passed to your `UserList` component is currently `undefined`.
In JavaScript, you can only use the `.map()` method on arrays. Because `users` is `undefined` (often due to data not finishing an API fetch yet, or the parent component forgetting to pass the prop), Node/React throws an error when it tries to read `.map`.
### How to Fix It
You can fix this in a few different ways, depending on how you want your application to behave.
#### Fix 1: Assign a Default Value (Recommended)
The cleanest way to handle this is to assign a default empty array to `users` in your component's parameters. If `users` is undefined, it defaults to…
13.2s1511 output tokens
Code Review
Please review the following Python function and suggest improvements for readability, performance, and best practices: def get_data(url, retries=3): import requests import time for i in range(retries):…
DeepSeek V4 Flash
Here's a comprehensive review with suggested improvements:
## Issues Identified:
1. **Import at wrong location** - Imports inside functions are inefficient and non-standard
2. **Bare `except:` clause** - Catches all exceptions including `KeyboardInterrupt`, `SystemExit`
3. **Missing error handling granularity** - Should distinguish between retryable and non-retryable errors
4. **Duplicate sleep logic** - Same sleep in `else` and `except` blocks
5. **Unnecessary variable** - `data` is only used once
6. **Inefficient list building** - Manual loop instead of list comprehension
7. **Hardcoded error message** - No logging or error context
8. **Missing type hints** - No type annotations
9. **Fun…
12.6s987 output tokens
Gemini 3.1 Pro Preview
Here is a review of your function. While the original code works, there are several areas where it can be improved regarding **best practices**, **readability**, and **performance**.
### 1. Refactored Code
Here is the improved version of your function. I will explain the specific changes below.
```python
import time
import requests
import logging
from typing import Any
# Optional: Set up a logger
logger = logging.getLogger(__name__)
def get_data(url: str, retries: int = 3, delay: int = 2, timeout: int = 10) -> list[dict[str, Any]]:
"""
Fetches JSON data from a URL and extracts active items.
Args:
url: The API endpoint to fetch data from.
retries: Number o…
23.6s3094 output tokens
Frequently asked questions
- Which is cheaper, DeepSeek V4 Flash or Gemini 3.1 Pro Preview?
- Per 1M output tokens, DeepSeek V4 Flash is ¥49.21 and Gemini 3.1 Pro Preview is ¥2,144.4 on FastMetal (yen, before tax), so DeepSeek V4 Flash is cheaper.
- How do the context windows of DeepSeek V4 Flash and Gemini 3.1 Pro Preview compare?
- DeepSeek V4 Flash takes 1,048,576 tokens; Gemini 3.1 Pro Preview takes 1,048,576.
- Which ranks higher, DeepSeek V4 Flash or Gemini 3.1 Pro Preview?
- Gemini 3.1 Pro Preview ranks higher on the public arena (DeepSeek V4 Flash #78, Gemini 3.1 Pro Preview #9). Ranks move as the leaderboard updates.
- Can I use DeepSeek V4 Flash and Gemini 3.1 Pro Preview with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "deepseek-v4-flash" or "gemini-3.1-pro-preview" as the model. Each is billed at its own rate from the same prepaid balance.
Try both on one API key
Create an account and add credit to call DeepSeek V4 Flash and Gemini 3.1 Pro Preview from the browser chat and the API. No monthly fee.