Coding interview guide
Coding vs system design interviews: what changes and how to prep
Most software engineering loops mix two very different kinds of technical round. A coding interview asks you to write a correct, efficient solution to a well-defined problem. A system design interview asks you to shape an open-ended system and defend trade-offs. Preparing for one doesn't prepare you for the other, so here's how they differ and how to split your time.
Companies don't publish their rubrics. The comparison below is based on Meta's and Google's official interview prep pages where they exist, plus candidate reports and prep sites (sources at the end). Formats vary by company and level, so confirm your loop with your recruiter.
The two rounds side by side
| Coding interview | System design interview | |
|---|---|---|
| Prompt | Well-defined: inputs, outputs, constraints | Open-ended: "design a URL shortener" or "design a news feed" |
| Typical length | 45 minutes, one or two problems | 45-60 minutes, one problem |
| Medium | Shared code editor or doc, often without running code | Whiteboard or diagram tool; Meta says its design rounds now run in CoderPad with Mermaid diagrams |
| What you produce | Working code plus complexity analysis | Requirements, estimates, API, data model, architecture diagram, deep dives |
| Is there a right answer? | Yes, usually an optimal approach | No; several designs can pass if the trade-offs are sound |
| Who drives | Interviewer sets the problem; you solve it | You drive; the interviewer probes |
Meta's own prep post puts it plainly: design interviews "almost never involve coding." The skills overlap less than people expect.
How each is graded
Coding
Interviewers look at problem solving, code quality, testing and communication. Meta's guidance says "it's better to have non-optimal but working code than just an idea." Google's says interviewers look at "the thought process versus the answer itself." Failing modes are concrete: no working solution, wrong complexity, bugs you didn't catch.
System design
Interviewers look at whether you scope the problem, make reasonable estimates, choose components for stated reasons, and go deep where it matters (storage, consistency, scaling, failure). Meta's prep post says good answers "compare and contrast different approaches." The usual failure modes are vaguer: drawing boxes without justifying them, never discussing trade-offs, or running out of time before any depth.
Who gets which round, by level
This is the pattern candidates and prep sites report for large tech companies. It is not a published rule, and smaller companies vary more.
| Level | Coding | System design |
|---|---|---|
| Intern / new grad | Most of the loop | Usually none, or a light design question |
| Mid-level (about 2-5 years) | Two or more rounds | Often one round, sometimes optional |
| Senior | Two rounds is common | One or two rounds, weighted heavily for level |
| Staff and above | Fewer rounds | Two rounds is common, sometimes including low-level design of infrastructure |
One prep site's summary of Meta: coding decides whether you're hired, design decides your level. Google's coding rounds carry the most weight at every level, with system design added for experienced candidates.
How the prep differs
- Coding prep is repetition. You learn a finite set of patterns (two pointers, BFS, heaps, DP and so on) and drill them until you can apply them under a clock. Progress is easy to measure: did you solve it in time?
- System design prep is building judgment. You learn building blocks (caches, queues, sharding, replication), a repeatable structure for the 45 minutes, and a handful of classic designs. Progress is harder to measure, so mock interviews matter more.
- Coding practice can be solo. A problem set and a timer get you far.
- Design practice needs a listener. Explaining trade-offs out loud to someone who pushes back is the skill being tested.
Splitting prep time by level
These are starting points, not rules. Shift toward whichever side is weaker for you.
| Target level | Coding | System design | Behavioral |
|---|---|---|---|
| New grad | About 80% | About 5% | About 15% |
| Mid-level | About 60% | About 25% | About 15% |
| Senior | About 45% | About 40% | About 15% |
| Staff and above | About 30% | About 50% | About 20% |
A combined eight-week plan (mid-level or senior)
- Weeks 1-3: coding patterns daily from one problem list (see Blind 75 vs NeetCode 150). Two evenings a week, learn system design building blocks.
- Weeks 4-5: keep coding at a lighter pace with timed sets. Learn a repeatable design structure, such as System Design LLM's 45-minute system design framework, and work two classic designs a week.
- Week 6: company-specific prep. Read about your target's format (for example our Meta and Google guides) and practice in that style.
- Weeks 7-8: mocks for both round types, alternating days, plus behavioral stories. Review mistakes rather than adding new material.
For the design side, System Design LLM's guides walk through classic problems like a URL shortener, news feed and rate limiter. System Design LLM is our sister app for system design practice; Interview LLM covers coding, and you can use it to get a worked solution with complexity analysis for a practice problem, then re-solve it yourself.
Sources (checked Nov 14, 2026)
- Meta Careers, "Preparing for your software engineering interview at Meta": metacareers.com/blog/preparing-for-your-software-engineering-interview-at-meta
- Meta Careers, "Hiring process" (interview FAQ): metacareers.com/hiring-process
- Google Careers, "Interviewing at Google: best practices, advice, and tips": google.com/about/careers/applications/interview-tips
- interviewing.io, "Meta interview questions and process": interviewing.io/meta-interview-questions
- interviewing.io, "Google interview questions and process": interviewing.io/google-interview-questions
FAQ
Do new grads get system design interviews?
Usually not a full one. Candidate reports for large tech companies say entry-level loops focus on coding and behavioral rounds, sometimes with a light design or object-oriented design question. Ask your recruiter; it's a normal question.
Can strong coding make up for a weak system design round?
At senior levels, rarely. Prep sites report that at companies like Meta, coding rounds largely decide whether you're hired, while design rounds weigh heavily on the level you're offered. A weak design round can mean a lower level rather than a rejection, but it varies by company.
Is low-level or object-oriented design the same as system design?
No. Object-oriented or low-level design asks for classes, interfaces and code structure for something like a parking lot or an elevator, and sits between the two. High-level system design is about services, storage, scaling and failure.