persistent systems coding interview
questions, leaked.
10 problems reported across recent persistent systems interviews. Top patterns: string, array, hash table. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Persistent Systems pulls from a tight, easy-leaning pool. Six of their ten problems are marked easy, and strings dominate the list: five string problems across all difficulties. You're looking at Group Anagrams, Valid Parentheses, Longest Substring Without Repeating Characters, and their variants. The trap is thinking easy means fast. String manipulation with hash tables and arrays requires clean logic under pressure. If you freeze on a string problem mid-assessment, StealthCoder runs invisibly and surfaces a working solution in seconds. But the real edge is drilling these ten problems until your hands move on muscle memory.
Top problems at persistent systems
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Minimum Bit Flips to Convert Number | EASY | 100.0 | 88% | Bit Manipulation |
| 02 | Group Anagrams | MEDIUM | 84.6 | 71% | Array · Hash Table · String |
| 03 | Palindrome Number | EASY | 73.2 | 59% | Math |
| 04 | Valid Parentheses | EASY | 73.2 | 42% | String · Stack |
| 05 | Two Sum | EASY | 64.2 | 56% | Array · Hash Table |
| 06 | Longest Substring Without Repeating Characters | MEDIUM | 64.2 | 37% | Hash Table · String · Sliding Window |
| 07 | Longest Palindromic Substring | MEDIUM | 64.2 | 36% | Two Pointers · String · Dynamic Programming |
| 08 | Valid Anagram | EASY | 64.2 | 67% | Hash Table · String · Sorting |
| 09 | Maximum Subarray | MEDIUM | 64.2 | 52% | Array · Divide and Conquer · Dynamic Programming |
| 10 | Merge Sorted Array | EASY | 64.2 | 53% | Array · Two Pointers · Sorting |
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 persistent systems OA. The proctor cannot see it. Screen share cannot detect it. Built because the OA filter rejects engineers who'd pass the on-site. That's a broken filter. This is the workaround.
Get StealthCoder- string5 · 50%
- array4 · 40%
- hash table4 · 40%
- sorting3 · 30%
- two pointers2 · 20%
- dynamic programming2 · 20%
- sliding window1 · 10%
- math1 · 10%
- stack1 · 10%
- bit manipulation1 · 10%
String handling is the primary axis here: five problems, all hitched to either hash-table lookups or array iteration. Array and hash-table problems (four each) follow close behind, often overlapping with strings. Two-pointers, dynamic programming, and sorting each appear two to three times but always as secondary tools, not the main pattern. Start with Two Sum and Valid Anagram to nail hash-table reasoning. Move to Group Anagrams and Longest Substring Without Repeating Characters, where you'll combine hash tables with string iteration. Longest Palindromic Substring and Maximum Subarray round out the medium tier and test your dynamic-programming instinct. Sorting and divide-and-conquer are backup skills. If you know strings and hash tables cold, you'll recognize eight of the ten patterns immediately. StealthCoder is your hedge for edge cases: the off-by-one bug in Longest Substring, the DP transition in Maximum Subarray, anything that breaks during screen share.
Companies with similar patterns
If you prepped for persistent systems, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass persistent systems.
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 because the OA filter rejects engineers who'd pass the on-site. That's a broken filter. This is the workaround. Works on HackerRank, CodeSignal, CoderPad, and Karat.
persistent systems interview FAQ
Should I prioritize string problems for Persistent Systems?+
Yes. Five of ten problems involve strings, and they're mixed across difficulties. Start with Valid Parentheses and Valid Anagram to warm up, then tackle Longest Substring Without Repeating Characters and Group Anagrams. These two alone will cover half your test surface.
How important are hash-table problems here?+
Critical. Hash tables appear in four problems and often pair with strings or arrays. Two Sum is your foundation. Group Anagrams, Valid Anagram, and Longest Substring all hinge on fast lookups. Spend time on hash-map construction and character-count patterns.
Do I need to practice dynamic programming for this assessment?+
It shows up in two problems: Maximum Subarray and Longest Palindromic Substring. Both are medium difficulty. If you're tight on time, focus on strings and hash tables first, then return to DP. It's not the primary filter.
What's the difficulty split and how should I prepare?+
Six easy, four medium, zero hard. The easy problems are your confidence builder and speed check. Don't slack on them. The medium tier (Group Anagrams, Maximum Subarray, Longest Substring) will separate you from other candidates. Drill both tiers fully.
Is two-pointers worth studying separately for this role?+
It appears in two problems, both paired with other topics. Merge Sorted Array and Longest Palindromic Substring use two-pointers, but it's not the core skill. Learn it as a technique within those specific problems rather than as an isolated unit.