gRPC Interview Questions

Checkout Vskills Interview questions with answers in gRPC to prepare for your next job role. The questions are submitted by professionals to help you to prepare for the Interview.

Q.1 What is gRPC?

gRPC (gRPC Remote Procedure Calls) is a high-performance, open-source framework developed by Google that allows you to build scalable, distributed systems by enabling remote procedure calls (RPC) between client and server applications.

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Q.2 How does gRPC differ from traditional REST APIs?

gRPC uses HTTP/2 for transport, Protocol Buffers (Protobuf) for serialization, and supports full-duplex streaming, whereas REST typically uses HTTP/1.1 and JSON, and is limited to request-response communication.

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Q.3 What are Protocol Buffers in gRPC?

Protocol Buffers (Protobuf) is a language-agnostic binary serialization format used by gRPC to serialize structured data, providing faster and more efficient data transmission compared to JSON or XML.

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Q.4 Explain the key features of gRPC.

Key features include language-agnostic, support for bi-directional streaming, load balancing, pluggable authentication, timeout and cancellation, and backward-compatible updates via Protocol Buffers.

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Q.5 What are the different types of RPCs supported by gRPC?

gRPC supports four types of RPCs: Unary RPCs, Server streaming RPCs, Client streaming RPCs, and Bidirectional streaming RPCs.

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Q.6 How does gRPC handle versioning and backward compatibility?

gRPC relies on Protocol Buffers, which support backward compatibility through the use of field numbering and optional fields, allowing schema evolution without breaking existing clients.

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Q.7 What is the role of HTTP/2 in gRPC?

HTTP/2 in gRPC provides multiplexing, flow control, header compression, and server push, which improves performance, supports multiple concurrent calls, and enables full-duplex streaming.

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Q.8 Describe the concept of streaming in gRPC.

Streaming in gRPC allows the server, client, or both to send a stream of messages over a single connection. This can be used for handling large data transfers or real-time data processing.

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Q.9 How does gRPC handle errors?

gRPC uses status codes (similar to HTTP status codes) to communicate errors. These codes, along with optional error messages, are returned in the gRPC response metadata.

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Q.10 What is the significance of service definitions in gRPC?

Service definitions in gRPC are written in a .proto file, defining the RPC methods that can be called remotely, the request and response message types, and the service interface that clients will use.

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Q.11 How can you secure gRPC communications?

gRPC supports TLS/SSL for securing communications. Additionally, it supports token-based authentication, such as OAuth2, and pluggable authentication mechanisms.

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Q.12 What is the role of the gRPC stub?

The gRPC stub acts as a client-side proxy that allows the client to make remote procedure calls as if they were local function calls, handling the communication details with the server.

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Q.13 Explain how gRPC handles load balancing.

gRPC provides client-side load balancing through a pluggable API. It supports various strategies like round-robin, pick-first, and more complex custom load balancers.

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Q.14 How does gRPC handle service discovery?

gRPC can integrate with service discovery systems (like Consul or etcd) using client-side load balancing and name resolvers to dynamically discover and route requests to available services.

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Q.15 What is gRPC Gateway?

gRPC Gateway is a plugin that allows you to expose gRPC services as RESTful APIs by translating RESTful HTTP calls into gRPC calls, enabling easy integration with existing HTTP/JSON-based services.

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Q.16 How do you implement client-side streaming in gRPC?

In client-side streaming, the client sends a stream of messages to the server using a streaming request method, and the server responds once all the client messages have been received.

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Q.17 What are the advantages of using gRPC over JSON-based communication?

gRPC offers better performance due to binary serialization (Protobuf), lower network overhead, built-in code generation for multiple languages, and support for advanced features like streaming and multiplexing.

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Q.18 What is deadline propagation in gRPC?

Deadline propagation in gRPC allows you to set a timeout for an RPC call. This timeout is propagated from the client to the server, ensuring that if the client is willing to wait only for a specific period, the server respects that deadline.

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Q.19 How do you implement server-side streaming in gRPC?

In server-side streaming, the server sends a stream of responses to the client after receiving a single request. The client reads from this stream until the server indicates the end of the stream.

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Q.20 What is the significance of Interceptors in gRPC?

Interceptors in gRPC are used to implement cross-cutting concerns like logging, authentication, and monitoring by intercepting the execution of RPCs on the client or server side, without modifying the core business logic.

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Q.21 What are the main components of a gRPC architecture?

The main components are the client, server, service definition (.proto file), stubs (client-side), skeletons (server-side), and the gRPC runtime, which handles communication between the client and server.

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Q.22 How do you define a service in a .proto file for gRPC?

A service is defined in a .proto file using the service keyword, followed by the service name and the RPC methods it supports, specifying input and output message types.

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Q.23 What is reflection in gRPC, and why is it useful?

Reflection in gRPC allows clients to query server metadata, such as available services and methods, at runtime. It is useful for tooling, dynamic clients, and when the .proto files are not available.

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Q.24 Explain the concept of a gRPC channel.

A gRPC channel is a long-lived connection to a gRPC server over which multiple RPCs can be sent. It manages connection setup, load balancing, and credentials.

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Q.25 How does gRPC handle message compression?

gRPC supports message compression using algorithms like gzip. Clients and servers can negotiate and apply compression to reduce the size of transmitted messages.

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Q.26 What are the different load balancing strategies available in gRPC?

gRPC supports several load balancing strategies, including round-robin, pick-first, least connection, and custom load balancers defined by the user.

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Q.27 Can you explain the role of metadata in gRPC?

Metadata in gRPC is a collection of key-value pairs that can be sent with RPC calls. It is used for passing additional information like authentication tokens, trace IDs, or custom headers.

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Q.28 How does gRPC handle backward compatibility?

gRPC achieves backward compatibility through Protocol Buffers by ensuring that message fields are optional, using reserved keywords, and maintaining field numbering.

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Q.29 What is gRPC-Web, and when would you use it?

gRPC-Web allows gRPC services to be consumed by web browsers. It’s used when you want to use gRPC in frontend applications where HTTP/2 support may be limited.

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Q.30 How can you monitor and debug gRPC services?

Monitoring and debugging gRPC services can be done using logging, tracing (e.g., OpenTelemetry), metrics collection, and gRPC reflection for service discovery.

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Q.31 Explain the concept of "channel pooling" in gRPC.

Channel pooling refers to reusing gRPC channels to avoid the overhead of repeatedly creating and destroying channels. This improves efficiency, especially in high-throughput scenarios.

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Q.32 What are the challenges associated with using gRPC in a microservices architecture?

Challenges include handling backward compatibility, service discovery, load balancing, security, observability, and managing the complexity of a strongly-typed contract.

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Q.33 How does gRPC ensure data integrity during transmission?

gRPC ensures data integrity using checksums provided by the underlying HTTP/2 protocol, and can further enhance security with TLS to prevent data tampering.

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Q.34 What is "context" in gRPC, and how is it used?

Context in gRPC is used to control RPC lifecycles, such as deadlines, cancellations, and passing metadata. It’s a critical mechanism for managing RPC calls' state and control flow.

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Q.35 How do you handle large payloads in gRPC?

Large payloads in gRPC can be handled through streaming, which allows data to be broken into chunks, or by adjusting the maximum message size settings.

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Q.36 Can gRPC be used with non-Protobuf serialization formats?

Yes, while Protobuf is the default, gRPC can be used with other serialization formats by defining custom marshallers and unmarshallers for the desired format.

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Q.37 Explain the difference between synchronous and asynchronous calls in gRPC.

Synchronous calls block the client until a response is received, while asynchronous calls return immediately, allowing the client to continue other work while waiting for the response.

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Q.38 How do you implement authentication in gRPC?

Authentication in gRPC can be implemented using TLS/SSL, token-based mechanisms like OAuth2, or by using metadata to pass credentials (e.g., API keys).

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Q.39 What is a "long-lived" gRPC stream, and how do you manage it?

A long-lived gRPC stream remains open for extended periods to handle continuous data flow between client and server. Managing it involves handling connection drops, backpressure, and resource cleanup.

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Q.40 What are the performance tuning techniques for gRPC services?

Performance tuning in gRPC can involve optimizing Protobuf message sizes, adjusting gRPC channel options (like max message size and keepalive settings), using load balancing, and employing efficient threading models on the server side.

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Q.41 What are the different types of streaming in gRPC, and when would you use each?

gRPC supports Unary (no streaming), Server-side streaming, Client-side streaming, and Bidirectional streaming. Use Server-side streaming when the server needs to send multiple responses, Client-side streaming when the client sends multiple requests, and Bidirectional streaming for full-duplex communication.

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Q.42 How does gRPC handle deadlines and timeouts?

gRPC allows clients to set a deadline for how long they are willing to wait for an RPC to complete. The server can check this deadline and abort the RPC if it exceeds the client's deadline.

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Q.43 What are gRPC interceptors, and how do they work?

Interceptors are middleware components in gRPC that can intercept and modify incoming or outgoing RPC calls. They are used for logging, authentication, metrics collection, and error handling.

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Q.44 Can you explain how gRPC manages resource cleanup for streaming RPCs?

gRPC manages resource cleanup by ensuring that streams are properly closed after use. Developers should handle errors and cancellations correctly and use defer statements (in languages like Go) or finally blocks to clean up resources.

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Q.45 What are the security implications of using gRPC over plain HTTP/2 instead of HTTPS?

Using gRPC over plain HTTP/2 (without TLS) exposes the communication to potential security threats like man-in-the-middle attacks, eavesdropping, and data tampering. Always use HTTPS to secure gRPC communications.

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Q.46 How do you implement custom error handling in gRPC?

Custom error handling in gRPC can be implemented by defining custom status codes or using rich error models with Protobuf to include detailed error information, such as error type and context.

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Q.47 What is gRPC’s support for retries, and how do you configure it?

gRPC supports automatic retries for failed RPCs. You can configure retry policies, including the number of retries, backoff strategy, and conditions for retrying, using service configuration files.

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Q.48 How does gRPC handle cross-language support?

gRPC provides cross-language support by generating client and server code from the same .proto file in multiple languages, ensuring consistent communication protocols across different platforms.

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Q.49 What are some common pitfalls when designing gRPC services?

Common pitfalls include not handling streaming correctly, improper use of deadlines and timeouts, ignoring backward compatibility in Protobuf definitions, and not securing communications with TLS.

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Q.50 How do you test gRPC services?

gRPC services can be tested using unit tests with mock services or clients, integration tests with in-process servers, and end-to-end tests using tools like gRPCurl or Postman’s gRPC support.

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Q.51 What is the role of "context" in gRPC and how do you pass it between calls?

The "context" in gRPC is used to carry deadlines, cancellations, and other request-scoped data between calls. It is passed from the client to the server with each RPC call, and can be used to cancel ongoing operations.

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Q.52 How can you handle versioning of gRPC APIs?

Versioning in gRPC can be managed by creating new versions of service definitions in .proto files, using package names or namespaces, or by maintaining backward compatibility with optional fields and reserved field numbers.

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Q.53 What are the differences between gRPC and SOAP?

gRPC is a modern, high-performance RPC framework using HTTP/2 and Protobuf, while SOAP is an older, XML-based protocol over HTTP with more overhead. gRPC is more efficient and supports streaming, whereas SOAP is more heavyweight and complex.

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Q.54 How do you handle large messages in gRPC?

Large messages in gRPC can be handled by increasing the maximum message size limit, using streaming to send data in chunks, or optimizing the message format to reduce size.

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Q.55 What is gRPC C++ vs gRPC C-core, and when would you choose one over the other?

gRPC C++ is a higher-level wrapper around the gRPC C-core, which is a portable, high-performance core implementation of gRPC. Choose gRPC C++ for easier integration with C++ applications, and C-core for lower-level, language-neutral performance optimizations.

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Q.56 What are some strategies for migrating from REST to gRPC?

Strategies include running gRPC and REST services in parallel, using gRPC Gateway to expose gRPC services as RESTful endpoints, and gradually converting REST clients to use gRPC.

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Q.57 Can you explain how bidirectional streaming works in gRPC with an example use case?

Bidirectional streaming allows both the client and server to send and receive a stream of messages. An example use case is a chat application where messages are continuously sent and received by both the client and server.

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Q.58 How do you ensure gRPC services are highly available and fault-tolerant?

Ensure high availability and fault tolerance by using client-side load balancing, retries with backoff strategies, deploying multiple service instances, and using health checks and circuit breakers.

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Q.59 What are the performance benchmarks for gRPC compared to REST?

gRPC typically outperforms REST in terms of latency, throughput, and resource usage due to its binary serialization with Protobuf, multiplexing over HTTP/2, and lower overhead.

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Q.60 How can gRPC be used in a polyglot microservices environment?

gRPC is ideal for polyglot microservices because it allows services written in different languages to communicate seamlessly through the consistent use of .proto definitions, enabling interoperability and efficient cross-language communication.

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