instabase coding interview
questions, leaked.
2 problems reported across recent instabase interviews. Top patterns: array, stack, union find. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
Instabase's coding assessment is lean but dense. With only two problems reported, you're looking at one medium and one hard, and they span eight distinct patterns. The hard problem layers array, stack, union-find, and monotonic-stack logic together. The medium asks you to build a trie from scratch. There's no room for half-measures here. If you blank mid-OA, StealthCoder runs invisibly and surfaces a working solution in seconds, so you're never stuck.
Top problems at instabase
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Subarray With Elements Greater Than Varying Threshold | HARD | 100.0 | 45% | Array · Stack · Union Find |
| 02 | Implement Trie (Prefix Tree) | MEDIUM | 100.0 | 68% | Hash Table · String · Design |
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 instabase 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- array1 · 50%
- stack1 · 50%
- union find1 · 50%
- monotonic stack1 · 50%
- hash table1 · 50%
- string1 · 50%
- design1 · 50%
- trie1 · 50%
The topic spread is deceptive. Instead of drilling one skill, Instabase tests whether you can stitch multiple patterns together in a single problem. The hard problem, 'Subarray With Elements Greater Than Varying Threshold,' demands you understand monotonic-stack mechanics and union-find efficiency simultaneously. The medium, 'Implement Trie,' is a classic design problem that tests your ability to code a data structure cleanly under pressure. Array and stack skills dominate, but don't skip union-find or trie. Your prep should focus on problems that combine multiple techniques, not isolated drills. If you hit the hard problem live and the monotonic-stack + union-find combo doesn't click, StealthCoder is your hedge.
Companies with similar patterns
If you prepped for instabase, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass instabase.
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.
instabase interview FAQ
How many union-find problems should I solve before the Instabase OA?+
Union-find appears in their harder problem but as one layer of a multi-pattern challenge. Solve 3 to 5 pure union-find problems to internalize path compression and union by rank, then shift to problems combining union-find with stacks or arrays.
Is 'Implement Trie' enough prep for the design half of the assessment?+
The trie problem is their only reported design ask, so yes, nailing trie insertion, search, and prefix logic is critical. Build it a few times from memory to own the implementation. Trie depth and character mapping will be tested.
Should I study monotonic stack before or after learning union-find?+
Start with monotonic stack. It appears with array and stack patterns, which are more foundational. Once you're confident, layer union-find problems on top. Their hard problem fuses both, so expect you to know each before tackling them together.
What if I only have time to drill one topic for Instabase?+
Pick monotonic stack. It's embedded in their hard problem and is less intuitive than basic stack logic. Trie is learnable in a few hours of focused coding, but monotonic-stack fluency takes time.
Can I pass with just string and hash-table knowledge?+
No. String and hash-table support the trie problem, but the harder problem requires array, stack, union-find, and monotonic-stack mastery. Both are tested, so both must be solid.