# CDP Knowledge Test vs System Design interview prep

The clearest difference is ads: CDP Knowledge Test at none against System Design interview prep's shown. System Design interview prep's advantage is update cadence (monthly vs every 3 months). On price, in-app purchases, device support and iOS requirement there is nothing between them.

Both are free to download. CDP Knowledge Test sells 2 in-app purchases, starting at $11.99 per month and System Design interview prep sells 5 in-app purchases, starting at $3.99 per 7 days. Whichever you choose, the download price is not the number that matters.

CDP Knowledge Test ships an update every 3 months, System Design interview prep monthly. The most recent releases landed on September 10, 2026 and September 26, 2026 respectively.

## The numbers

| Metric | CDP Knowledge Test | System Design interview prep |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[1.0 (2 ratings)](https://appshunter.io/ios/app/system-design-interview-prep/id6756310915/reviews)** |
| Number of ratings | — | **2** |
| Positive reviews | — | 0.0% of reviews |
| In-app purchases | Yes | Yes |
| Ads | **No** | Yes |
| Update frequency | Every 3 months | **Monthly** |
| Monetization | — | Free with in-app purchases |
| Size | 9 MB | 89 MB |
| Requires iOS | **17.2** | 17.6 |
| Devices | iPhone | **iPhone, iPad** |
| Age rating | 4+ | 4+ |
| Developer | [Cargo Teleport Inc](https://appshunter.io/developer/1761832181) | [Abdelhak El Moussaoui](https://appshunter.io/developer/1827690433) |

## What reviewers say

### CDP Knowledge Test

[App page](https://appshunter.io/ios/app/cdp-knowledge-test/id6740606245)

**Features:** macOS Compatibility

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium monthly subscription | $11.99 | per month |
| Lifetime version | $24.99 | one-time |


### System Design interview prep

[App page](https://appshunter.io/ios/app/system-design-interview-prep/id6756310915)

This app simulates system design interviews with an AI interrogator and interactive scenarios. Practice real-world architecture problems, receive instant feedback, and track your progress to ace your next tech interview.

**Highlights:** Interactive War Room for architecture scenarios, AI Interrogator challenges design decisions, Realistic system design interview questions, Daily practice drills for skill sharpening, Detailed performance analytics, Instant feedback and best practice learning

**Features:** macOS Compatibility

**In-app purchases (5)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Unlimited access | $3.99 | per 7 days |
| Unlimited access | $4.99 | per 7 days |
| Unlimited access | $6.99 | per month |
| Unlimited access | $12.99 | per month |
| Unlimited access | $99.99 | per year |


## Frequently asked questions

### Is CDP Knowledge Test free?

CDP Knowledge Test is free to download, with in-app purchases available.

### Is System Design interview prep free?

System Design interview prep is free to download, with in-app purchases available.

### Do CDP Knowledge Test or System Design interview prep have ads?

System Design interview prep shows ads; CDP Knowledge Test does not.

### Which is updated more often, CDP Knowledge Test or System Design interview prep?

CDP Knowledge Test ships an update every 3 months, and System Design interview prep monthly. Most recently, CDP Knowledge Test was updated on September 10, 2026 and System Design interview prep on September 26, 2026.

---

*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*