Cloudflare coding interview
questions, leaked.
10 problems reported across recent Cloudflare interviews. Top patterns: array, design, math. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Cloudflare's interview is heavy on systems thinking and array manipulation. You're looking at 10 problems across mostly medium difficulty, with design questions woven throughout. The core pattern is obvious: they want to see if you can build things (Design Circular Queue, LRU Cache, Design Hit Counter) and manipulate arrays under constraints (3Sum, 4Sum, Number of Islands). One hard math problem rounds it out. If you blank on a tricky design question mid-assessment, StealthCoder runs invisibly and surfaces a working implementation in seconds. Your real prep is nailing the seven array-based problems and understanding when to use hash tables or linked lists to back your designs.
Top problems at Cloudflare
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Design Circular Queue | MEDIUM | 100.0 | 53% | Array · Linked List · Design |
| 02 | 3Sum | MEDIUM | 94.4 | 37% | Array · Two Pointers · Sorting |
| 03 | 4Sum | MEDIUM | 94.4 | 38% | Array · Two Pointers · Sorting |
| 04 | Reaching Points | HARD | 84.3 | 34% | Math |
| 05 | Design a Stack With Increment Operation | MEDIUM | 84.3 | 80% | Array · Stack · Design |
| 06 | Design Hit Counter | MEDIUM | 74.5 | 69% | Array · Binary Search · Design |
| 07 | Number of Islands | MEDIUM | 69.9 | 62% | Array · Depth-First Search · Breadth-First Search |
| 08 | LRU Cache | MEDIUM | 63.9 | 45% | Hash Table · Linked List · Design |
| 09 | Game of Life | MEDIUM | 55.5 | 71% | Array · Matrix · Simulation |
| 10 | Fizz Buzz | EASY | 55.5 | 74% | Math · String · Simulation |
Frequencies derived from public community-tagged interview reports. Click a row to view on LeetCode.
You have a week, maybe less. You can't out-grind the list above. StealthCoder runs invisibly during the actual Cloudflare OA. The proctor cannot see it. Screen share cannot detect it. Built by an engineer at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share.
Get StealthCoder- array7 · 70%
- design4 · 40%
- math2 · 20%
- queue2 · 20%
- linked list2 · 20%
- two pointers2 · 20%
- sorting2 · 20%
- matrix2 · 20%
- simulation2 · 20%
- stack1 · 10%
Arrays dominate the distribution with seven problems, but they're rarely pure array drills. Most are array-backed design challenges or spatial problems (matrix traversal, game simulation). The second tier reveals the actual interview focus: design patterns appear in four problems, which means Cloudflare cares less about raw algorithm speed and more about whether you can articulate trade-offs and build clean interfaces. Two-pointers (3Sum, 4Sum) and sorting appear together, suggesting they test sorting-based optimization. The single hard problem is a math question that requires insight, not memorization. If you've practiced basic array sorting and two-pointer logic, you're halfway there. The real gap for most candidates is design system questions like LRU Cache or the circular queue. That's where StealthCoder becomes your safety net on the live OA: if the design question throws you, a working solution appears on screen while the proctor sees nothing.
Companies with similar patterns
If you prepped for Cloudflare, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Cloudflare.
Memorizing every problem above in a week is a fantasy. StealthCoder is the hedge: an AI overlay that's invisible during screen share. It reads the problem on screen and surfaces a working solution in under 2 seconds. Built by an engineer at a top-10 tech company who can solve these problems cold but didn't want to trust himself in a 90-minute screen share. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Cloudflare interview FAQ
How many design problems should I practice before the Cloudflare OA?+
Four of the ten problems are design-focused (LRU Cache, Design Circular Queue, Design Hit Counter, Design a Stack). Drill at least three full design patterns end-to-end: understand the data structure backing, trade-offs between approaches, and clean code. Know when to use a hash table plus linked list versus an array-based implementation.
Should I focus on array problems or design first?+
Start with design. Seven problems touch arrays, but most are array-backed design or spatial traversal (matrix, islands). If you can't design a circular queue or LRU Cache, raw array sorting won't save you. Spend 60 percent on design clarity, 40 percent on two-pointer and sorting refresher.
Is one hard problem enough to worry about before the OA?+
The hard problem is a math question (Reaching Points). It's one of ten, so it's not the bottleneck. Master the eight medium problems first. If you have time, read the hard problem the night before to spot if it's a pattern you've seen. If not, that's exactly when StealthCoder solves it in real-time during your assessment.
What's the fastest way to prepare for the array and two-pointer problems?+
You have 3Sum and 4Sum in the top problems. Both use sorting plus two pointers. Do 3Sum cold, understand the sort-and-pivot approach, then 4Sum is the same pattern nested. That covers your two-pointer surface area. Array problems beyond that are mostly embedded in design or matrix traversal, not standalone drills.
Should I memorize LRU Cache or understand the logic?+
Understand it. LRU Cache is in the top problems and requires you to explain eviction policy and O(1) operations. Walk through the hash table plus doubly-linked list trade-off out loud. You don't need to code it from memory, but if you freeze mid-interview, knowing the structure buys you time to recover instead of panic-coding.