Confluent coding interview
questions, leaked.
12 problems reported across recent Confluent interviews. Top patterns: hash table, array, string. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Confluent's coding interview leans hard on hash tables and design patterns. Twelve problems total, split evenly between medium and hard, with seven of them pivoting around hash-table logic. You're looking at LRU Cache, Time Based Key-Value Store, and Design Authentication Manager as the heavy hitters, all of which demand you build efficient data structures under time pressure. Array and string problems round out the rest. If you hit a design problem mid-assessment and blank on the approach, StealthCoder runs invisibly during screen share and surfaces a working solution in seconds.
Top problems at Confluent
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | LRU Cache | MEDIUM | 100.0 | 45% | Hash Table · Linked List · Design |
| 02 | Time Based Key-Value Store | MEDIUM | 93.9 | 49% | Hash Table · String · Binary Search |
| 03 | Valid Sudoku | MEDIUM | 87.0 | 62% | Array · Hash Table · Matrix |
| 04 | Minimum Time to Eat All Grains | HARD | 83.3 | 39% | Array · Two Pointers · Binary Search |
| 05 | Sudoku Solver | HARD | 81.2 | 64% | Array · Hash Table · Backtracking |
| 06 | Design Authentication Manager | MEDIUM | 65.0 | 58% | Hash Table · Linked List · Design |
| 07 | Regular Expression Matching | HARD | 65.0 | 29% | String · Dynamic Programming · Recursion |
| 08 | Debounce | MEDIUM | 65.0 | 92% | |
| 09 | Combination Sum | MEDIUM | 59.2 | 75% | Array · Backtracking |
| 10 | Wildcard Matching | HARD | 59.2 | 30% | String · Dynamic Programming · Greedy |
| 11 | Count Subarrays With Median K | HARD | 51.1 | 46% | Array · Hash Table · Prefix Sum |
| 12 | Number of Atoms | HARD | 51.1 | 65% | Hash Table · String · Stack |
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 Confluent OA. The proctor cannot see it. Screen share cannot detect it. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know.
Get StealthCoder- hash table7 · 58%
- array5 · 42%
- string4 · 33%
- design3 · 25%
- linked list2 · 17%
- doubly linked list2 · 17%
- binary search2 · 17%
- matrix2 · 17%
- backtracking2 · 17%
- dynamic programming2 · 17%
Hash tables dominate this interview. Seven out of twelve problems explicitly test hash-table reasoning, often paired with linked lists or design constraints. LRU Cache and Design Authentication Manager are both medium-difficulty but conceptually dense, requiring you to combine doubly-linked lists with hash maps to hit O(1) operations. String problems like Regular Expression Matching and Wildcard Matching are hard and recurse into dynamic programming territory, so they're either your strength or your weakness with no middle ground. Array-based problems cluster around two-pointer and binary-search patterns. Skip the linked-list and backtracking problems if you're short on time, but don't skip hash tables or design. They're 70% of the interview. If you've drilled hash-map problems but design patterns still feel foreign, StealthCoder is your hedge when the live assessment throws a novel caching or state-management problem at you.
Companies with similar patterns
If you prepped for Confluent, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Confluent.
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. Made by a working FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Confluent interview FAQ
How many hash-table problems should I solve before the Confluent assessment?+
At least five. Seven of the twelve problems tested here hinge on hash-table mechanics. Drill LRU Cache, Time Based Key-Value Store, and Design Authentication Manager by name. The other four should cover basic map operations, collision handling, and prefix-sum patterns.
Is design worth studying for Confluent if I only have a week?+
Yes, urgently. Three out of twelve problems are explicitly design-based, and two of those are medium difficulty, not hard. LRU Cache and Design Authentication Manager appear in most interview reports. You can't afford to skip them, and they're closer to medium than they look.
Should I study dynamic programming if I'm weak at strings?+
Only if you have time after hash tables and design. Two hard string problems, Regular Expression Matching and Wildcard Matching, both use dynamic programming or recursion. They're lower frequency than the hash-table cluster, so they're your second-week focus.
What's the difficulty split I should expect?+
Exactly half medium, half hard. Six of each. The medium problems aren't easier conceptually, they just have fewer edge cases. Expect design and hash-table problems at medium; expect hard variants in strings and arrays with multi-step logic.
Can I skip backtracking and linked lists to save time?+
Mostly. Backtracking and linked lists each appear in only two problems, and linked lists only show up paired with hash tables in design contexts. Backtracking doesn't dominate. Focus on hash tables, design, arrays, and strings first, then backtracking if you have bandwidth left.