This time Snowflake ‘s experience of Backend SDE's electronics is quite "engineering-oriented". The question itself does not pursue fancy algorithms, but each round asks: If this is the back-end system you write every day, how would you design it?
The following is what I roughly recorded during the auxiliary stage, organized into a complete review for the reference of students preparing for Snowflake/back-end system direction.
Coding Round 1: Key-Value Store with transaction support (constant complexity)
Question ontology:
Implement a simple key-value store, supporting:
Get(key)Set(key, value)Remove(key)
This part is quite basic and can be completed quickly using HashMap.
Follow-up (real test points):
Based on the above, the following transaction operations are supported:
Begin()Commit()Rollback()
And requires operationThe time complexity is O(1)(At least in an evenly distributed sense).
What does the interviewer really care about?
This question is not a test of API, but a test of:
- You are right Transaction/Rollback/State Isolation Do you have engineering intuition?
- Can you think of it? Log / stack / shadow copy / multiple versions These design tools
- Have you considered the cost of rollback in advance instead of only finding it difficult to return it after writing it?
Throughout the process, the interviewer will continue to ask:
- What if begin is nested?
- Is the semantics of commit a merge or an overwrite?
- How to ensure that the entire data is not scanned during rollback?
If you just write an implementation that "runs", it's easy to be questioned and get stuck.
Coding Round 2: Tree height + optimal solution under structural modification
Basic questions:
Given a tree, calculate the height of the tree.
This is a very standard DFS/BFS question with almost no difficulty.
Follow-up (difficulty increases significantly):
Given a target height, ask how many nodes need to be deleted at least to make the height of the tree ≤ height.
After a node is deleted, all its child nodes will directly become the child nodes of the node's parent node.
What is being tested on this question?
This question is quite Snowflake-esque:
- The surface is a tree
- Actually taking the exam Global optimal strategy after structural changes
The key difficulties are:
- Deleting a node does not mean "the entire subtree is gone"
- RatherThe child nodes will move up and participate in the height calculation again.
So this question is not simply "cut the deepest node", but requires you to think:
- The deletion of which nodes will have the greatest impact on the overall height
- How to make decisions from the bottom up instead of brute force simulations
The interviewer will focus on your:
- The ability to disassemble ideas
- Can you clearly explain why deleting it this way is optimal?
- Rather than how beautiful the code is
System Design: Quota Management Service (very close to the real backend)
Topic:
Design a quota management service to support:
- Apply for quota
- Return quota
- Each user has a quota limit
- Need to consider the situation of "applying for quota but not using it"
Interviewer's style
The interviewer in this round is quite strict and is trying to catch you throughout the process. Back-of-the-envelope:
- How many concurrent users are there?
- How granular is the quota?
- How to recycle unused quota after timeout?
- Is it push recycling or lazy recycling?
Obviously I’m not asking you to draw a very “beautiful” architecture diagram, but look at:
- Will you ever Real business constraints Set off
- Are you aware of issues such as resource waste, lock contention, and delayed consistency?
If you only stay at the level of "using Redis + DB + API", you will be questioned in depth.
This round is almost
这一轮几乎There are no traditional behavioral interview template questions(For example, "What should I do if I have a disagreement with my colleagues?")
Instead:
- The whole process revolves around the projects you have done
- A detailed look at design decisions, trade-offs, and failure experiences
The most impressive question
If your boss gives you a business metric and asks you to be responsible for improving the company's performance on this metric, what will you do?
If the goal is to improve by 20%, how do you break it down?
This question is quite typical of Snowflake:
- No consideration of emotion management
- The test is How engineers are responsible for the business
Interviewer concerns include:
- Will you first define the composition of the metric?
- Can it be broken down into actionable sub-indicators?
- How to evaluate which changes are “high ROI”
Even though it is not a standard STAR,It is still very useful to use the STAR structure to organize answers.
Summary: What kind of person is Snowflake Backend SDE looking for?
In summary, my biggest feeling is:
- I don’t like “question-answering players” very much.
- Highly valued engineering thinking + business understanding + design and disassembly capabilities
If you are preparing for Snowflake or a similar back-end/data system company, it is recommended to focus on preparing:
- Stateful system design (transaction, quota, resource management)
- Can be asked in-depth data structure questions (not the kind that can be written in one line)
- How to connect technology decisions with business metrics
Writing the code is only the starting point, and clearly explaining "why it is designed this way" is the key.
Why engineering interviews need real-time interview assistance
If you are preparing for a back-end interview with strong engineering and strong questioning like Snowflake, in fact, many people are stuck not because they “can’t write”, but because they have divergent ideas on the spot and are interrupted by continuous follow-ups. What we do Interview assistance services , can help you stabilize your engineering thinking: help you quickly clarify data structure and complexity trade-offs in the Coding wheel, remind you of key boundary conditions (concurrency, recycling, excess, abnormal paths) in real time during System Design, and help you quickly organize scattered experiences into expressions with logic, indicators, and decision-making basis in Behavioral/Business Question. Especially in interviews like Snowflake that loves to dig deep into the rationality of design, there is an "engineering perspective calibrator standing behind you" that can often determine whether you are overwhelmed by questioning, or whether you can firmly control the interview rhythm in your own hands.
