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HubSpot interview notes, page 1 of 3

Large Enterprises

Most of these HubSpot write-ups come from Software Engineers (26), then Product Managers (3) and Machine Learning Engineers (1). The most reported rounds are the system design round (13), the technical phone screen (7), the hiring manager screen (4) and the behavioral / leadership round (3).

30 interview notes · updated Jul 2026

HubSpot·Software Engineer·Onsite - System Design / Architecture

Apr 2026
System design round at HubSpot focused entirely on building a GPU-backed inference API. It was one of the more exhausting design sessions I've had, covering basically everything from batching strategy to multi-tenant isolation in a single go.
  • Design a GPU-backed inference API for serving deep learning models. Walk through the API design (sync vs async), request schema and versioning, routing, batching strategy, model loading and cold-start handling, and multi-model hosting on shared GPUs.
  • How would you handle autoscaling across heterogeneous GPU nodes, and what placement strategy would you use for routing inference requests?
  • What observability would you build into this system? Specifically around latency, throughput, and GPU metrics.
  • How would you implement rate limiting and multi-tenant isolation in this inference platform?
  • How would you approach failure handling, including retries, timeouts, and canary or A/B rollouts for new model versions?

“This is a big one and I didn't pace myself well.”

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HubSpot·Software Engineer·Technical Phone Screen

Apr 2026
HubSpot software engineering interview that focused on a practical banking API design problem. The question covered account creation, deposits, and transfers with real constraints around atomicity and error handling. Pretty meaty for a single session.
  • Design and implement a set of APIs for creating a bank account, depositing funds into it, and transferring money between two accounts. Your solution needs to handle concurrent balance updates atomically and deal with failure cases properly.

“The transfer part is where things get interesting and also where I probably spent too long.”

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HubSpot·Software Engineer·Onsite - System Design / Architecture

Apr 2026
Round 2 at HubSpot was a system design problem centered on a weather service. The core challenge was handling stale data from an external API that only updates hourly, while keeping the frontend fresh within a 10-minute window.
  • Design a weather service where the frontend must display data no older than 10 minutes, given that the upstream data source (NWS) publishes updates hourly as a zip file. How do you handle cases where the upstream hasn't refreshed yet and your fetch returns stale data?

“The stale data handling part is where I think I undersold myself.”

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HubSpot·Software Engineer·Technical Phone Screen

Apr 2026
HubSpot technical phone screen for a software engineering role. The whole thing was basically one big coding problem with a follow-up that kept expanding, which I wasn't fully ready for.
  • Implement an LRU cache in Python as a decorator that takes a max size and memoizes a function's results. It needs to handle positional args, *args, and **kwargs so that semantically equivalent calls map to the same cache key, including unhashable arguments. It should support eviction of the least recently used entry, a clear() method, and a cache_info() method.
  • Follow-up: add save() and load() methods to persist the cache to a JSON file without using pickle. How do you encode the cache keys and values, handle return values that aren't JSON-serializable, and manage versioning across saves?

“I started with the obvious OrderedDict approach and got the basic LRU logic down fine.”

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HubSpot·Software Engineer·Onsite - Behavioral / Leadership

Apr 2026
Behavioral round at Hubspot for a SWE role, just the one question about cross-cultural collaboration. Pretty standard stuff, nothing too surprising.
  • Can you describe a time you collaborated with someone from a different background than your own?

“I had a story ready but it felt thin once I started telling it.”

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HubSpot·Machine Learning Engineer·Recruiter / HR Screen

Apr 2026
Recruiter screen for a senior ML Engineer role at HubSpot, pretty much just a comp conversation.
  • What are your base salary expectations for this role, and what compensation structure (base, bonus, equity) would you be open to? Do you have a hard floor, and is there flexibility depending on scope or level?

“Pretty standard opener for a recruiter call.”

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HubSpot·Software Engineer·Technical Phone Screen

Apr 2026
HubSpot coding screen focused on a hash map design problem around employee management constraints. Pretty straightforward premise but the dual-constraint angle tripped me up a bit on the first pass.
  • Implement an 'add employee to a company' operation that validates two rules: no more than 5 employees per position per company, and no employee can hold more than 2 positions at the same company. Process a list of these operations in order and return success or invalid with the specific rule that was violated for each.

“My first instinct was to reach for a nested structure and I wasted a couple minutes mentally organizing it before realizing two flat hash maps keyed by (company, position) and (company, employee) respectively would just...”

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HubSpot·Software Engineer·Onsite - System Design / Architecture

Apr 2026
Did a system design round for a software engineer role at HubSpot. The focus was on designing Netflix, but the interviewer kept drilling into schema choices and cache behavior rather than the high-level architecture, which I wasn't fully prepared for.
  • Design the Netflix system. Walk through your schema design and how you'd handle caching, including what happens when cache miss rates spike.

“I spent too long on the broad strokes (services, load balancing, CDN) and the interviewer kept pulling me back to the data model and cache behavior.”

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HubSpot·Software Engineer·Technical Phone Screen

Apr 2026
Got a coding screen at HubSpot that was pretty much a straightforward array manipulation problem. Nothing crazy, but the in-place constraint is where people slip up if they're not careful.
  • Given an integer array and a target value, remove all occurrences of that value in place and return the count of remaining elements. The first k elements of the modified array should hold the valid values in any order. Must run in O(n) time with O(1) extra space.

“Two pointers is the move here and I did get there, but I fumbled around for a bit first thinking about a second array before remembering the space constraint.”

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HubSpot·Software Engineer·Onsite - System Design / Architecture

May 2026
System design round at HubSpot for a software engineering role. The prompt was basically 'build Netflix' which sounds exciting until you realize how many moving parts they actually want you to cover in 45 minutes.
  • Design a large-scale video streaming platform similar to Netflix. Walk through the full system including user auth, content catalog, search, recommendations, video processing, DRM, adaptive streaming, CDN strategy, storage, playback sessions, APIs, multi-region failover, observability, and cost optimization for millions of concurrent users.

“This is one of those questions where the scope is so wide you could spend three hours on it and still feel like you skimmed everything.”

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