Recently, a classmate just walked the entire Visa SDE interview process consists of four rounds in total, and the difficulty is obviously progressive. The first round is more basic communication, but the real technical challenge actually begins with the second round of coding. If you understand the question structure in advance, it will actually be much easier to prepare.
This article simply sorts out the interview process and two core coding questions, which is a relatively complete review.
Visa SDE interview overall process
The whole process consists of four rounds, and the rhythm is still a relatively standard North American tech interview structure:
- Phone Screening
- Coding Interview
- Technical/System Discussion
- Hiring Manager / Behavioral
The first round is mainly about basic communication, and the actual testing of technical capabilities is in the later rounds.
Round 1: Phone Screening
Basic communication wheel
The first round is relatively easy In summary, mainly to allow the interviewer to quickly understand your background. The questions basically revolve around past project experiences, technology stacks used, and teamwork.
Common topics include:
Past project experience
Technology stack mastery
Teamwork Case
Why you want to join Visa
This round is overall behavioral + background discussion.
Interview preparation advice
It is recommended to prepare several complete STAR stories in advance. For example, the projects we have done, the problems we encountered, how we solved them, and the final results. As long as the expression is clear and the logic is smooth, it is generally not too difficult.
Round 2: Coding Interview
Technology wheel
The second round begins with a standard coding interview. The interviewer mainly tests the basic abilities of data structures and algorithms.
There were two questions given in this round, with the difficulty level ranging from medium to medium+. The interesting thing is that the questions are closely integrated with Visa's payment business scenarios, and are not completely abstract algorithm questions.
Coding Question 1
Transaction Fraud Detection
The first question is a relatively typical payment risk control scenario. The question is given a list of transactions. Each transaction contains information such as timestamp, amount, merchant_id, country and card_id. Systems need to detect potential fraud based on transaction patterns.
Decision rules
There are two main rules:
More than 3 transactions on the same card within 5 minutes
Transactions from different countries appear on the same card within 1 hour
As long as any one of these conditions is met, the transaction needs to be marked as suspicious transaction.
Problem-solving ideas
The core idea is actually to group by card_id, and then perform time window detection in the transaction record of each card.
A common approach is to first use defaultdict to group transactions by card_id. Then sort each set of transactions according to timestamp. After sorting, the transaction frequency within 5 minutes can be detected through the sliding window.
For detection of different countries, you can directly compare the countries of adjacent transactions. If there is a country change within an hour, it can be marked as an anomaly.
This question is essentially a data processing problem, focusing on how to efficiently maintain time windows and avoid repeated scanning. The overall complexity comes mainly from sorting and is roughly O(n log n).
Coding Question 2
Payment Processing Queue
The second question is more like a simplified version of the system design question, which requires the implementation of a transaction processing system. The system needs to support priority processing of transactions and be able to process transactions in batches.
Business rules
Transactions are divided into two priorities based on amount:
Transactions with amounts greater than 1000 are high priority
Transactions with amounts less than or equal to 1000 belong to normal priority
High-priority transactions need to be processed first, while ordinary transactions are processed in FIFO order.
Implementation ideas
A more intuitive approach is to use two different data structures to manage transactions.
High-priority transactions can be stored using max heap, so that transactions with the largest amount can be taken out first every time. Ordinary transactions can be stored in order using an ordinary queue.
The system can design a PaymentProcessor class to provide two core methods: add_transaction and process_batch. The former is responsible for adding transactions and classifying them according to the amount, and the latter is responsible for processing transactions in batches according to priority.
When implemented, the processing logic is usually to fetch high-priority transactions from the heap first, and if there are insufficient high-priority transactions, replenish them from the ordinary queue.
What to do if you get stuck in the coding interview
When many students are doing VO or live coding, it’s not that they don’t know how to write, but that their ideas suddenly stop and their time is easily delayed. We usually do some things here Interview assistance , such as real-time voice reminders, idea reminders, key step reminders, etc. Many students relied on this method to successfully complete the questions in key VO sessions, and finally successfully got the offer.
If you are currently preparing for OA or VO from companies such as Visa, Amazon, TikTok, and Google, it will actually be much easier if you are familiar with the question structure and interview rhythm in advance.
