Technical Interview Questions & Answer Guides

Model Candidate Answer

Java Garbage Collection automatically manages memory allocation and deallocation. Memory is divided into Young Generation (Eden + Survivor spaces) and Old Generation. G1GC (Garbage-First) divides memory into equal regions and prioritizes regions with the most garbage. ZGC (Z Garbage Collector) is a low-latency garbage collector designed to handle terabytes of heap memory with pause times under 1 millisecond.

Sample Code / Configuration Snippet

// Example: JVM GC options for low-latency G1 collector
java -XX:+UseG1GC -XX:MaxGCPauseMillis=200 -Xms4g -Xmx4g -jar app.jar

RECRUITER EVALUATION RUBRIC Look for candidates who understand heap memory tuning (-Xms, -Xmx) and can explain how GC pause time affects high-throughput REST APIs.

Model Candidate Answer

synchronized is an implicit lock mechanism built into JVM block statements or method signatures. ReentrantLock is an explicit lock implementation from java.util.concurrent.locks that provides features like lock polling with timeout (tryLock), interruptible lock acquisition, and fair locking options.

Sample Code / Configuration Snippet

Lock lock = new ReentrantLock();
if (lock.tryLock(1000, TimeUnit.MILLISECONDS)) {
    try {
        // Critical section
    } finally {
        lock.unlock();
    }
}

RECRUITER EVALUATION RUBRIC Candidate should explain thread starvation, deadlock prevention strategies, and when to choose ReentrantLock over synchronized.

Model Candidate Answer

Node.js runs on a single-threaded Event Loop backed by libuv. Microtasks (process.nextTick, Promise callbacks) execute immediately after the current operation finishes before moving to the next Event Loop phase. Macrotasks (setTimeout, setInterval, setImmediate, I/O callbacks) execute in specific queue phases.

Sample Code / Configuration Snippet

console.log("Start");
setTimeout(() => console.log("Timeout"), 0); // Macrotask
Promise.resolve().then(() => console.log("Promise")); // Microtask
console.log("End");
// Output: Start -> End -> Promise -> Timeout

RECRUITER EVALUATION RUBRIC Candidate should explain why blocking CPU operations inside Node.js event loop degrades API concurrency.

Model Candidate Answer

Optimize aggregation by placing $match and $sort operations at the very beginning of the pipeline so MongoDB can leverage compound indexes. Avoid early $unwind or $group operations which expand dataset size in memory before filtering.

Sample Code / Configuration Snippet

db.candidates.aggregate([
    { $match: { technology: "MERN", status: "processed" } }, // Indexed first
    { $sort: { created_at: -1 } },
    { $limit: 20 },
    { $project: { name: 1, email: 1, ctc: 1 } }
]);

RECRUITER EVALUATION RUBRIC Look for practical experience with <code>db.collection.explain("executionStats")</code> and index usage strategies.

Model Candidate Answer

ReAct is a prompting & execution framework where an LLM agent alternates between generating Reasoning thoughts ("Thought: I need to search the database") and performing Action tool calls ("Action: query_database"). The agent observes tool outputs ("Observation: 5 records found") to reach a final answer autonomously.

Sample Code / Configuration Snippet

class ReActAgent:
    def step(self, user_prompt):
        thought = self.llm.generate_thought(self.context)
        tool_call = self.llm.parse_tool(thought)
        observation = tool_call.execute()
        return self.synthesize(observation)

RECRUITER EVALUATION RUBRIC Candidate should articulate how agent memory state is preserved across function calling loops and how infinite tool loops are prevented.

Model Candidate Answer

Azure Managed Identities provide an automatically managed identity in Microsoft Entra ID (Azure AD) for resources like Azure App Service or VMs. It eliminates the need for developers to store database passwords or storage keys in application source code or configuration files.

Sample Code / Configuration Snippet

// C# Azure SDK with DefaultAzureCredential
var client = new SecretClient(
    new Uri("https://myvault.vault.azure.net/"), 
    new DefaultAzureCredential()
);

RECRUITER EVALUATION RUBRIC Check if the candidate has configured System-assigned vs. User-assigned Managed Identities in production pipelines.

Model Candidate Answer

The Service Container is a powerful tool for managing class dependencies and performing dependency injection. Classes request dependencies via constructor type-hints, and the container automatically resolves and injects instances at runtime without manual instantiation.

Sample Code / Configuration Snippet

public function __construct(CandidateRepositoryInterface $repository) {
    $this->repository = $repository;
}

RECRUITER EVALUATION RUBRIC Candidate should understand binding interfaces to concrete implementations in ServiceProviders for testability.

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Technical Interview Questions Bank

How does Garbage Collection (GC) work in Java, and what is the difference between G1 and ZGC?

Model Candidate Answer

Explain the Synchronized Keyword vs. ReentrantLock in Concurrent Java Applications.

Model Candidate Answer

What is the Event Loop in Node.js, and how do Microtasks differ from Macrotasks?

Model Candidate Answer

How do you optimize MongoDB Aggregation Pipelines for millions of candidate documents?

Model Candidate Answer

What is ReAct (Reason + Act) architecture in Autonomous Agentic AI frameworks?

Model Candidate Answer

How do Managed Identities work in Azure, and how do they eliminate hardcoded connection strings?

Model Candidate Answer

How does Dependency Injection and Service Container work in PHP Frameworks like Laravel?

Model Candidate Answer