My 2025 Oracle Software Engineer Interview Questions and Answers
After going through so many interview rounds, I finally received an offer to be a Software Engineer at Oracle. Now that I can relax while waiting to start my new job, I want to share my experience.
I'll walk you through my actual interview process and the questions I was asked, then tell you about my preparation strategies, interview tips, and provide some sample answers to common questions. Without further ado, let's get started.
Oracle Software Engineer Interview Process and Actual Questions
Interview Stages and Timeline Overview
The number of interview rounds at Oracle can vary based on the position and level. The entire process typically includes a phone screen, a technical interview, a behavioral interview (BQ), and so on. Each stage is unique and tests a different set of skills.
Personally, my interview rounds went like this:
Round 1: A 30-minute phone screen.
Round 2: About half a month later, I had three back-to-back VOs that focused on system design, coding, and behavioral questions.
Offer: I received a verbal offer about two weeks later, followed by an HR call the next day.
My Oracle Interview Experience and Real Questions
Overall, I found that the interviewers at Oracle were generally very friendly, and some even seemed eager for me to pass. A number of the interviewers were also recent hires. However, the interview styles varied significantly across different rounds, with technical questions and behavioral questions (BQs) often mixed together. While the atmosphere was relaxed, the technical questions covered core concepts, with a difficulty level generally ranging from LeetCode easy to medium. My experience was that the system design round, in particular, heavily emphasized the analysis process and trade-offs, while the algorithm questions required a clear explanation of the logic. Actively communicating my thought process during the interview was crucial.
HR Call
This phone call was mainly about my background and the company culture. The interviewer asked about my experience based on my resume, as well as some very basic questions like what I knew about the company and why I was interested in the position.
Coding Interview
The interviewer was very nice, but their questioning style was a bit unconventional. The interview started with a simple behavioral question before getting to the main point. The problem was very simple: processing a log string. The task was to deserialize, validate, and then output it as required. The interviewer then asked if the input was a list or an array of logs and even hinted that a log might be split into multiple lines. He then continued to ask follow-up questions about how to search the logs, what data structures to use, and the pros and cons of different data structures.
During this round, it was clear the interviewer was very keen for me to pass. He seemed almost impatient to give me the answer as soon as he asked a question. This made me nervous because it meant I had to answer quickly so he wouldn't feel like he was giving me the solution. My mind was racing the entire time.
Technical Interviews
The first technical interview consisted entirely of casual coding questions and some informal behavioral questions.
System Design
This round asked me to design a file conversion system to convert a PDF into a JSON file using an existing model that processes one page at a time. I had to address scalability, error handling, and performance optimization. The interviewer asked detailed questions to evaluate my problem-solving skills and my ability to analyze trade-offs, and to explain the reasoning behind my final choice of approach. Overall, it felt very smooth and was a good experience. There were also some standard behavioral questions at the end.
Algorithm Questions
This round had two problems. The first was on Binary Search Trees: "Given a BST, write an algorithm to find the in-order successor (or predecessor) of a specified node. Explain the logic and provide pseudocode." The second was a Trie Tree application: "Implement an autocomplete system using a Trie data structure. The system should return a list of possible full words based on a partial input string." This round also ended with standard behavioral questions.
If you're concerned about getting too nervous or not being able to answer questions during an interview, I recommend Linkjob's AI Interview Copilot. It can listen to the interviewer's questions and provide you with an answer. You can also take a screenshot to have the AI solve coding questions, and it is invisible to the interviewer when you share your screen.
Oracle Software Engineer Interview Questions
When I prepared for the oracle software engineer interview, I wanted to know exactly what kinds of questions to expect. I found that the interviewers focused on a mix of coding, technical, system design, machine learning, and behavioral topics. Let me break down each area and share what I experienced.
Data Structures & Algorithms Interview Questions and Answers
Question 1: Given a binary tree, write a function to invert/reverse it. The inversion should swap the left and right children of every node in the tree.
What the interviewer wants to hear: The ability to quickly come up with a recursive solution and explain the time and space complexity.
Question 2: You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and nums2 respectively. Merge nums1 and nums2 into a single array sorted in non-decreasing order. The final sorted array should not be returned by the function, but instead be stored inside the array nums1.
My Approach: Use two pointers to traverse both arrays. Compare the elements pointed to by the two pointers, add the smaller element to the result, and then move the corresponding pointer.
Question 3: Given a string s, find the first non-repeating character in it and return its index. If it doesn't exist, return -1.
My Approach: Use a hash map to record the frequency of each character, then iterate through the string to find the first character with a count of 1.
Database & SQL Interview Questions and Answers
1. What are the different types of JOINs in SQL?
There are four primary types of JOINs in SQL, used to combine rows from two or more tables based on a related column between them:
INNER JOIN: Returns rows when there is at least one match in both tables. It only includes the rows with matching values.
LEFT JOIN (or LEFT OUTER JOIN): Returns all rows from the left table and the matched rows from the right table. If there's no match, the columns from the right table will be
NULL.RIGHT JOIN (or RIGHT OUTER JOIN): Returns all rows from the right table and the matched rows from the left table. If there's no match, the columns from the left table will be
NULL.FULL JOIN (or FULL OUTER JOIN): Returns all rows when there is a match in one of the tables. It combines the results of both
LEFTandRIGHTjoins.
2. Explain ACID properties in databases.
ACID is an acronym that stands for Atomicity, Consistency, Isolation, and Durability. These are a set of properties that guarantee the reliability of database transactions.
Atomicity: Ensures that a transaction is treated as a single, indivisible unit. Either all of the operations within the transaction succeed, or none of them do. If any part of the transaction fails, the entire transaction is rolled back.
Consistency: Guarantees that a transaction brings the database from one valid state to another. Data written to the database must be valid according to all defined rules, constraints, and triggers.
Isolation: Ensures that concurrent transactions do not interfere with each other. The result of a transaction is the same as if it were the only transaction running on the system.
Durability: Guarantees that once a transaction has been committed, it will remain in the database even in the event of a system failure (like a power outage).
3. What is database normalization?
Normalization is the process of organizing data in a database to reduce data redundancy and improve data integrity. The goal is to divide large tables into smaller, less redundant tables and define relationships between them.
The process is typically broken down into different Normal Forms (1NF, 2NF, 3NF, etc.). Moving to a higher normal form generally means you have less redundant data but may require more complex queries.
4. Write a query to find duplicate records.
A common way to find duplicate records is to use the GROUP BY clause with the HAVING clause. The GROUP BY clause groups rows that have the same values, and the HAVING clause filters these groups to show only those with a count greater than one.
SQL
SELECT
column1,
column2,
COUNT(*)
FROM
your_table
GROUP BY
column1,
column2
HAVING
COUNT(*) > 1;
5. What is the difference between clustered and non-clustered indexes?
Both clustered and non-clustered indexes are used to improve query performance, but they differ in how they store data.
Clustered Index: This type of index physically sorts the data rows in the table based on the key column(s). A table can have only one clustered index because the data can only be physically sorted in one way. The index itself is the data, which means it provides fast access to the data.
Non-Clustered Index: This index is a separate structure from the data. It contains the key column(s) and a pointer to the actual location of the data row. A table can have many non-clustered indexes. Think of it like a textbook's index: it points to the page where you can find the information, but it isn't the book itself.
System Design & Architecture Interview Questions and Answers
1. Design a URL Shortening Service like bit.ly
The goal is to design a service that takes a long URL and generates a unique, short URL, and then redirects users from the short URL to the original long one. The system must be highly available and scalable, especially for the read-heavy redirection part.
High-Level Design
The service has two main functionalities:
URL Shortening (Write Flow): A user submits a long URL to our service. We generate a unique short key and store the key-to-long-URL mapping in a database.
Redirection (Read Flow): A user accesses a short URL. We use the short key to look up the original long URL in our database and send a redirect (HTTP 301 or 302) to the user's browser.
Key Components & Design Choices
API & Key Generation: The service needs a key generation component. A simple auto-incrementing integer from a database can work, but a more scalable method is to generate a unique random string (e.g., a Base62 encoded string of a UUID or a unique counter). Base62 is a good choice because it uses digits, lowercase, and uppercase letters (62 characters), which allows for shorter keys.
Database: A key-value store is an excellent choice due to the simple data model (key: short_url, value: long_url). A NoSQL database like Cassandra or Redis is highly scalable for both reads and writes.
Caching: Redirections are far more frequent than shortenings. A cache like Redis or Memcached is critical. We would cache the most-requested short URLs to handle millions of requests per second without hitting the database.
Load Balancing & API Gateway: An API Gateway would handle incoming requests and direct traffic to either the shortening service or the redirection service, while a load balancer would distribute the load.
2. Design a Chat Application
The goal is to design a real-time messaging service, similar to WhatsApp or Slack, supporting one-on-one and group chats. The system must be highly available, scalable to millions of concurrent users, and provide a seamless user experience.
High-Level Design
The core of a chat application is its real-time communication. This is typically achieved using a persistent, bidirectional connection. The main flow involves a client sending a message to a server, which then delivers it to the recipient.
Client: The application on the user's phone or desktop.
API Server: Handles user authentication, friend lists, and offline message storage.
Real-time Communication Layer: Uses a protocol like WebSockets for a continuous connection between the client and the server, allowing for instant, low-latency message delivery.
Message Broker: A component like Kafka or RabbitMQ to handle message delivery asynchronously and reliably.
Database: A NoSQL database like MongoDB or Cassandra is a good fit for storing chat history due to its scalability and flexible schema, which can handle different message types (text, images, etc.).
Key Design Considerations
WebSockets vs. HTTP: WebSockets are the preferred choice over traditional HTTP because they maintain a persistent, bidirectional connection, avoiding the overhead and latency of frequent polling.
Fan-out for Group Chats: When a user sends a message to a group, the message needs to be delivered to all members. This is called a "fan-out." A message broker handles this efficiently by pushing the message to multiple queues for each group member.
Offline Messages: Messages sent to users who are offline are stored in a database and delivered once the user comes back online.
Scalability: The system is horizontally scalable. API servers, WebSocket servers, and database nodes can all be scaled out to handle increasing traffic.
3. How would you design a distributed cache?
A distributed cache is a system that stores frequently accessed data in a network of servers to improve application performance by reducing the load on the database.
Core Concepts
Cache Invalidation Strategies:
Write-Through: Data is written simultaneously to the cache and the database. This ensures consistency but can have higher write latency.
Write-Back: Data is written to the cache first and then flushed to the database later. This has low write latency but carries a risk of data loss if the cache node fails.
Read-Through: Data is populated in the cache on a read miss. This is a common and effective strategy.
Eviction Policies: When the cache is full, it needs a strategy to remove old data. Common policies include LRU (Least Recently Used), LFU (Least Frequently Used), and FIFO (First-In, First-Out).
Data Partitioning (Sharding): To distribute data across multiple cache nodes, you need a smart way to decide where to store each key. Consistent Hashing is a great solution because it minimizes the number of keys that need to be remapped when a cache node is added or removed, ensuring high availability.
High-Level Design
The cache sits between the application server and the database.
The application client requests data from the cache using a key.
A client library uses a hashing algorithm (like Consistent Hashing) to determine which cache node holds the data.
If the data is found (cache hit), it's returned immediately.
If the data is not found (cache miss), the application fetches the data from the database, populates the cache with the new data, and then returns the data to the user.
Scalability & Fault Tolerance
The design must be horizontally scalable. You can add more cache nodes to increase capacity. For fault tolerance, data can be replicated across multiple nodes. If one node fails, its replicas can take over, preventing data loss and service interruption.
Behavioral Questions
Based on my experience, these questions primarily assess soft skills. Interviewers look for my teamwork ability and whether I'm a good cultural fit for Oracle. The questions I was asked were mostly about past experiences, challenges I've faced, and how I handle conflicts. It's very important to communicate well and show a collaborative attitude when answering these, because Oracle places a strong emphasis on behavioral questions (BQ).
Here are some behavioral questions I remember:
Tell me about a time you solved a difficult problem.
How do you handle disagreements in a team?
Describe a situation where you had to learn something quickly.
What motivates you as an engineer?
How do you prioritize tasks when you have multiple deadlines?
Note: For BQ prep, it's helpful to focus on Oracle's official documents about ORACLE CODE OF ETHICS AND BUSINESS CONDUCT, as they outline their core values on page 5.
FAQ
What resources did you use to prepare?
My main focus was on platforms like LeetCode and HackerRank to practice algorithms and data structures. For system design, I read through common design questions and solutions on platforms like LeetCode's system design section and other online resources. I also reviewed core database concepts, which was especially helpful for Oracle.
How much focus was on soft skills and culture?
Behavioral questions were a significant part of the interview, often disguised within technical discussions. Interviewers were looking for my teamwork skills, my approach to problem-solving, and how I handle setbacks or conflicts. Demonstrating a collaborative attitude was very important.
Can I ask my own questions during the interview?
Absolutely! I always asked about team culture and growth opportunities. Interviewers appreciated my curiosity. Asking questions helped me learn more about the role and showed I cared about my future at Oracle.
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