For software engineers preparing for interviews
A curated directory for software engineering interview prep
PrepKit is a curated, open-source directory of software engineering interview preparation resources. Every listing shows its source and license, company pages record dated rules on AI use in interviews, and you can practice with a text interviewer that runs on your own API key.
Try a practice interviewText only, on your own OpenRouter API key. Sign in when you start.
Browse
Start from your role, topic, company or language
Company rules
Can you use AI in the interview? It depends on the company.
No reviewed company rules are published yet. Rows appear here as soon as an editor verifies a dated source.
AI-use policies change quickly. Ask your recruiter which interview round, if any, permits AI and which tools you may use. PrepKit is for practice before your interview. Do not use it as a live interview copilot.
Practice interviewer
Rehearse in text, on your own key
Pick a mode
Technical, behavioral, system design or GenAI system design. One question at a time, with follow-ups.
- Technical / coding
- Behavioral / STAR
- System design
- GenAI system design
Paste your provider key the first time you start
The key stays in this browser session and is sent directly to OpenRouter over TLS. PrepKit never receives or stores it. Your provider bills you for the tokens you use.
Answer in your own words
The free plan accepts 40 of your messages a day. Provider errors do not count against it, and your transcript survives a refresh or a sign-in.
Read a report tied to what you said
Each dimension is scored only when the report can point to your own words. If it cannot, it says not assessed instead of guessing.
You are asked to sign in only when you start.
Your key stays in this browser session for storage and is sent directly to OpenRouter over TLS. PrepKit does not receive it. Provider charges and retention terms apply.
Unverified practice feedback, not a hiring prediction.
Sample conversation
- InterviewerLet's start small. You need to design a rate limiter for a public API that serves about a thousand requests per second. Where would you begin?
- YouI'd first ask what we are protecting: fairness per client or total capacity. If it's per client, I'd keep a token bucket per API key in Redis with a TTL and check it at the edge, before the request reaches the service.
- InterviewerGood. What happens to your counters if Redis is unavailable for thirty seconds?
Sample report
- Correctness
- 3 of 4
- Named the token bucket and where it runs. Evidence: your first answer.
- Communication
- 4 of 4
- Asked a clarifying question before choosing a design.
- Trade-off reasoning
- Not assessed
- No evidence yet: the sample ends before the failure-mode answer.
- AI fluency
- Not assessed
- Not asked about in this short sample.
From the directory
Curated listings, each with its source
The first listings are still in editorial review. Nothing is published until its source and license are confirmed.
Pricing
Free to browse. Pay only for more practice and tracking.
Free
$0.00
No card, and no account to browse
- Browse and search the directoryIncluded
- Source credits, licenses, and AI-policy warningsIncluded
- Saved itemsNo limit
- Roadmap progress trackingUp to 25 tracked steps
- Practice interview messages40 practice messages a day
Pro Monthly
$20.00
$20.00 per month
Pro access that renews each month. You can cancel anytime from the billing portal.
- Browse and search the directoryIncluded
- Source credits, licenses, and AI-policy warningsIncluded
- Saved itemsNo limit
- Roadmap progress trackingNo limit
- Practice interview messagesNo limit
Lifetime
One-time$180.00
$180.00 once
The same Pro access for a single payment. Nothing renews.
- Browse and search the directoryIncluded
- Source credits, licenses, and AI-policy warningsIncluded
- Saved itemsNo limit
- Roadmap progress trackingNo limit
- Practice interview messagesNo limit
Pro Monthly and Lifetime give the same access. Licensed content, source credits, and policy warnings stay free for everyone. Practice has no daily limit on a paid plan, but abuse and provider limits still apply, and you pay your AI provider directly.
Polar processes payments as our merchant of record.
Open source
Open code, credited sources
License
PrepKit's code is free software under the GNU Affero General Public License v3.0. If you run a modified copy as a service, the same license asks you to publish your changes.
How we curate
- We embed only material whose license allows it, and we show the source, license and version we used.
- Share-alike material stays in its own marked section under the same license.
- Sites that do not allow reuse are linked by title and address only. We never scrape a rendered page.
- Submitted resources are reviewed by a person. Approval cannot be bought, and sponsored entries are labeled.
Questions
What first-time visitors ask
- Which coding platform or resource should I use?
- There is no single right answer, so PrepKit does not rank one platform above the rest. Search for your topic or language, filter by format and price, and open a listing to read where it comes from and under what license. Every listing links to the original resource.
- Where do I start with system design as a beginner?
- Open the system design topic and begin with the free, permissively licensed material listed there. When you want to talk it through, the practice interviewer has a system design mode that asks one question at a time and follows up on your answer.
- How do I prepare for behavioral rounds?
- Browse the behavioral topic for guides on structuring answers with the STAR method, then rehearse in the Behavioral / STAR practice mode. The report points to the exact lines of your answers it used, so you can see what came across and what did not.
- Can I use AI during a real interview?
- It depends on the company and often on the round. PrepKit records what each company has said publicly, with the source and the date it was checked, and marks a policy as unknown when the evidence is stale or unverified. Policies change quickly, so confirm with your recruiter before the interview. PrepKit is for practice beforehand, not for use during an interview.
- Which AI mock interview tools are useful?
- PrepKit's interviewer is a text practice tool that runs on your own API key: the key stays in your browser session and goes straight to the provider, which bills you directly. It asks one question at a time, avoids repeating recent questions, and returns feedback tied to your own words. It is practice feedback, not a prediction of how a real interview will go.
- Is PrepKit free, and do I need an account?
- Browsing, search and every resource page are free without an account. You sign in only to save favorites, track roadmap progress, start a practice interview or buy a plan. The free plan includes a daily practice allowance. Pro Monthly is $20.00 per month and Lifetime is $180.00 once, and both give the same access.
- Where does the content come from?
- Listings come from openly licensed sources that PrepKit is allowed to reuse, always shown with their source, license and version, and from resources people submit and an editor reviews. Sites that do not allow reuse are linked by title and address only. The code itself is open source under the AGPL-3.0.