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Integration / Apache Pulsar Interview questions

Explain the execution flow of a distributed transaction across microservices in AppDynamics?

In a microservices architecture, a single user-facing request often fans out across many independently deployed services, and AppDynamics reconstructs that entire path as one logical Business Transaction rather than a set of disconnected per-service metrics.

sequenceDiagram participant User participant Gateway as API Gateway (originating tier) participant Orders as Order Service participant Inventory as Inventory Service participant Payments as Payment Service participant Controller User->>Gateway: POST /checkout Gateway->>Gateway: Agent starts Business Transaction, generates correlation ID Gateway->>Orders: Call + singularityheader Orders->>Inventory: Call + singularityheader Orders->>Payments: Call + singularityheader Inventory-->>Orders: Response Payments-->>Orders: Response Orders-->>Gateway: Response Gateway-->>User: 200 OK Gateway-->>Controller: Report segment Orders-->>Controller: Report segment Inventory-->>Controller: Report segment Payments-->>Controller: Report segment Controller->>Controller: Reconcile segments into one cross-tier snapshot

Each service's own agent only knows about its own segment of the work; none of them individually sees the whole picture. It's the Controller, after receiving every tier's separately-reported segment tagged with the same correlation identifier, that stitches them together into a single transaction snapshot and a single flow-map path.

This is what lets a team looking at one slow checkout request see, in one view, that the Order Service itself was fast but it was blocked waiting nearly a full second on the Payment Service — a conclusion that would be nearly impossible to reach by looking at each service's isolated dashboards separately, since no single dashboard shows the full chain end to end.

Which component reconstructs the full cross-service transaction path?
Why is a single-service dashboard often insufficient for diagnosing cross-service latency?

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Explain about Apache Pulsar. What is AppDynamics? What is Apache Pulsar? What is a Pulsar broker? What is Application Performance Monitoring (APM)? What is Apache BookKeeper? What are the core components of the AppDynamics platform? What is the Controller in AppDynamics? What are tenants and namespaces in Pulsar? What is a topic in Pulsar? What is an App Agent in AppDynamics? What is a producer in Pulsar? What are the types of agents available in AppDynamics? What is a consumer in Pulsar? What is a Business Transaction in AppDynamics? What is a Tier in AppDynamics? What is a subscription in Pulsar? Define a partitioned topic in Pulsar? What is a Node in AppDynamics? What is a Business Application in AppDynamics? What is Pulsar's metadata store used for? What is the Application Flow Map? What are Pulsar Functions? What is Pulsar IO? What is a Health Rule? What is a Policy in AppDynamics? Describe geo-replication in Pulsar? What is a Transaction Snapshot? What is tiered storage in Pulsar? What is a non-persistent topic in Pulsar? Define baseline in AppDynamics? What is the Machine Agent used for? What are the subscription types in Pulsar? What is End User Monitoring (EUM)? What is message retention in Pulsar? What is schema registry in Pulsar? What is Database Visibility in AppDynamics? What are Backends in AppDynamics? List the core components of a Pulsar cluster? How do you create a topic in Pulsar? Describe the Metric Browser in AppDynamics? What is the difference between a Tier and a Node in AppDynamics? What is the difference between Pulsar and Kafka's storage architecture? How does Pulsar separate compute and storage? How does AppDynamics automatically discover Business Transactions? What is the difference between automatic and custom Business Transaction match rules? Why is Pulsar considered multi-tenant by design? What is the difference between Shared and Exclusive subscriptions? How does AppDynamics correlate a transaction across multiple tiers? How does Key_Shared subscription maintain ordering? Why is the singularityheader important in transaction correlation? When should you use Failover subscription instead of Exclusive? How does AppDynamics decide when to capture a transaction snapshot? What is dynamic baselining and how does it work? What is the difference between a ledger and a segment in BookKeeper? How does Pulsar achieve message deduplication? Why does the Java Agent use byte-code instrumentation? Explain the internal working of AppDynamics' byte-code instrumentation? Why do brokers in Pulsar not store data locally? What happens when a broker crashes in Pulsar? What is a Service Endpoint in AppDynamics? How does namespace bundle splitting work? What is an Information Point? What is the difference between backlog quota and retention policy? What is a Data Collector in AppDynamics? When should you use custom match rules instead of automatic discovery? When should you use a Reader instead of a Consumer? How does topic compaction work in Pulsar? What is the difference between Slow, Very Slow, and Stalled transactions? Why is ensemble size different from write quorum in BookKeeper? How does AppDynamics calculate Average Response Time (ART)? What is the difference between the Machine Agent and the Network Agent? What is the difference between persistent and non-persistent topics? How does Pulsar handle delayed message delivery? What is an Adaptive Session in AppDynamics? What happens when a consumer negatively acknowledges a message? What is a thread dump and when does AppDynamics capture one automatically? Explain the lifecycle of a message in Pulsar from produce to acknowledge? How would you troubleshoot a suspected memory leak using AppDynamics? How can you optimize Pulsar for high-throughput workloads? What are custom extensions for the Machine Agent? How do you troubleshoot a growing backlog in Pulsar? How does the Cluster Agent monitor Kubernetes environments? What is the difference between SaaS and On-Premises Controller deployments? Explain the execution flow of topic ownership failover in Pulsar? How can you optimize BookKeeper storage costs using tiered storage? How can you reduce AppDynamics agent overhead in a production environment? What is Business iQ / Analytics in AppDynamics? Explain the internal working of Pulsar transactions? How does AppDynamics integrate with ITSM tools like ServiceNow or PagerDuty? Which is better for exactly-once processing: idempotent producers or transactions, and why? What is the AppDynamics REST API used for? How do you troubleshoot unbalanced load across brokers? Explain the lifecycle of a namespace bundle from creation to split? Explain the lifecycle of an alert from health rule violation to notification? How can you optimize consumer throughput with Key_Shared subscriptions? What is the difference between Warning and Critical health rule severities? Explain the execution flow of a Pulsar Function processing a message? What are Instrumentation exclude rules and why would you use them? How do you troubleshoot message duplication in a Pulsar producer? Explain the execution flow of a distributed transaction across microservices in AppDynamics?
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