gRPC for internal services in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a gRPC service method in the proto file.

HLD

service UserService {
  rpc GetUser (GetUserRequest) returns ([1]);
}

Drag options to blanks, or click blank then click option'

AGetUserResponse

BUserRequest

CUserResponseStream

DGetUserStream

Attempts:

3 left

💡 Hint

Common Mistakes

Using request message as response type

Using streaming types incorrectly

The gRPC method must specify the response message type. Here, GetUserResponse is the correct response message.

2fill in blank

medium

Complete the code to create a gRPC client stub in the service implementation.

HLD

const client = new [1](address, grpc.credentials.createInsecure());

Drag options to blanks, or click blank then click option'

AUserServiceClient

BUserServiceStub

CGrpcClient

DUserClient

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect client class name

Confusing stub with client

The client stub class is generated with the service name followed by 'Client'. Here, UserServiceClient is correct.

3fill in blank

hard

Fix the error in the server handler function signature for unary gRPC call.

HLD

function getUser([1], callback) {
  // handler logic
}

Drag options to blanks, or click blank then click option'

Astream

Brequest

Ccontext

Dcall

Attempts:

3 left

💡 Hint

Common Mistakes

Using request instead of call

Using stream for unary calls

In gRPC server handlers, the first argument is the call object containing request data and metadata.

4fill in blank

hard

Fill both blanks to configure a gRPC server with TLS credentials.

HLD

const server = new grpc.Server();
const creds = grpc.ServerCredentials.[1](keyCertPairs, [2]);
server.bindAsync(address, creds, () => server.start());

Drag options to blanks, or click blank then click option'

AcreateSsl

BcreateInsecure

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using createInsecure for TLS

Setting client cert flag incorrectly

To enable TLS, use createSsl with key-cert pairs and set the second argument to false to disable client certificate verification.

5fill in blank

hard

Fill all three blanks to implement a server streaming gRPC method handler.

HLD

function listUsers([1]) {
  const call = [2];
  users.forEach(user => call.[3](user));
  call.end();
}

Drag options to blanks, or click blank then click option'

Acall

Bnew grpc.ServerWritableStream()

Cwrite

Dsend

Attempts:

3 left

💡 Hint

Common Mistakes

Creating new stream object manually

Using send instead of write

The handler receives a call object for streaming. Use call.write() to send each message.

Practice

1. What is the main advantage of using gRPC for communication between internal services?

easy

A. It provides fast and efficient communication using HTTP/2 and Protocol Buffers.

B. It uses plain text JSON for easy debugging.

C. It requires no schema definition for messages.

D. It only works for external client-server communication.

Solution

1. Step 1: Understand gRPC communication basics

   gRPC uses HTTP/2 for transport and Protocol Buffers for message serialization, making it fast and efficient.

2. Step 2: Compare options with gRPC features

   Options A and B are incorrect because gRPC uses binary Protocol Buffers, not JSON, and requires schema definitions. It only works for external client-server communication. is wrong because gRPC is often used internally.

3. Final Answer:

   It provides fast and efficient communication using HTTP/2 and Protocol Buffers. -> Option A

4. Quick Check:

   gRPC speed and efficiency = It provides fast and efficient communication using HTTP/2 and Protocol Buffers. [OK]

Hint: Remember gRPC uses HTTP/2 + Protocol Buffers for speed [OK]

Common Mistakes:

• Confusing gRPC with REST using JSON
• Thinking gRPC doesn't need schemas
• Assuming gRPC is only for external APIs

2. Which of the following is the correct way to define a gRPC service method in a Protocol Buffers (.proto) file?

easy

A. service UserService { function GetUser (UserRequest) returns UserResponse; }

B. service UserService { call GetUser (UserRequest) returns UserResponse; }

C. service UserService { method GetUser (UserRequest) -> UserResponse; }

D. service UserService { rpc GetUser (UserRequest) returns (UserResponse); }

Solution

1. Step 1: Recall gRPC service syntax in .proto files

   The correct syntax uses rpc MethodName(RequestType) returns (ResponseType); inside a service block.

2. Step 2: Match options to correct syntax

   Only service UserService { rpc GetUser (UserRequest) returns (UserResponse); } matches the exact gRPC syntax. Others use incorrect keywords like function, method, or call.

3. Final Answer:

   service UserService { rpc GetUser (UserRequest) returns (UserResponse); } -> Option D

4. Quick Check:

   gRPC method syntax = service UserService { rpc GetUser (UserRequest) returns (UserResponse); } [OK]

Hint: Look for 'rpc' keyword inside service block [OK]

Common Mistakes:

• Using 'function' or 'method' instead of 'rpc'
• Omitting parentheses around request/response types
• Misplacing 'returns' keyword

3. Given this gRPC service definition snippet:

service OrderService {
  rpc CreateOrder (OrderRequest) returns (OrderResponse);
}

What happens when a client calls CreateOrder with invalid data that violates the schema?

medium

A. The server returns a validation error before processing the request.

B. The server accepts the request and processes it anyway.

C. The client call fails at compile time due to schema mismatch.

D. The server crashes due to invalid input.

Solution

1. Step 1: Understand gRPC schema validation

   gRPC uses Protocol Buffers which enforce message structure. Invalid data is rejected by the server with an error.

2. Step 2: Evaluate options based on gRPC behavior

   The server returns a validation error before processing the request. is correct because the server validates input and returns errors. The server accepts the request and processes it anyway. is unsafe and incorrect. The client call fails at compile time due to schema mismatch. is wrong because client code compiles but runtime validation happens. The server crashes due to invalid input. is incorrect as servers handle errors gracefully.

3. Final Answer:

   The server returns a validation error before processing the request. -> Option A

4. Quick Check:

   gRPC input validation = The server returns a validation error before processing the request. [OK]

Hint: Invalid data triggers server validation error, not crash [OK]

Common Mistakes:

• Assuming client compile-time failure for invalid data
• Thinking server processes invalid requests
• Believing server crashes on bad input

4. You notice that your internal gRPC service calls are slow and sometimes timeout. Which of the following is the best first step to debug this issue?

medium

A. Remove Protocol Buffers and switch to JSON messages.

B. Rewrite all services to use REST instead of gRPC.

C. Check network latency and HTTP/2 connection health between services.

D. Increase client timeout without investigating.

Solution

1. Step 1: Identify common causes of gRPC slowness

   Network issues and HTTP/2 connection problems often cause delays in gRPC calls.

2. Step 2: Evaluate debugging approaches

   Check network latency and HTTP/2 connection health between services. is the best first step to diagnose root cause. Options B and C are drastic changes without diagnosis. Increase client timeout without investigating. ignores the problem source.

3. Final Answer:

   Check network latency and HTTP/2 connection health between services. -> Option C

4. Quick Check:

   Debug gRPC slowness = Check network latency and HTTP/2 connection health between services. [OK]

Hint: Start debugging network and HTTP/2 before changing code [OK]

Common Mistakes:

• Jumping to rewrite services without diagnosis
• Ignoring network as a cause
• Blindly increasing timeouts

5. You are designing an internal microservices system using gRPC. Which design choice best improves scalability and fault isolation?

hard

A. Avoid using Protocol Buffers and send raw JSON over gRPC.

B. Define small, focused gRPC services with clear method boundaries and use load balancing.

C. Use gRPC only for external APIs and REST internally.

D. Combine all functionality into one large gRPC service to reduce network calls.

Solution

1. Step 1: Understand microservices design principles with gRPC

   Small, focused services with clear APIs improve scalability and fault isolation. Load balancing helps distribute load.

2. Step 2: Evaluate design options

   Define small, focused gRPC services with clear method boundaries and use load balancing. aligns with best practices. Combine all functionality into one large gRPC service to reduce network calls. creates a monolith, hurting scalability. Use gRPC only for external APIs and REST internally. wastes gRPC benefits internally. Avoid using Protocol Buffers and send raw JSON over gRPC. breaks gRPC efficiency by avoiding Protocol Buffers.

3. Final Answer:

   Define small, focused gRPC services with clear method boundaries and use load balancing. -> Option B

4. Quick Check:

   Microservices + gRPC best practice = Define small, focused gRPC services with clear method boundaries and use load balancing. [OK]

Hint: Small services + load balancing = scalable gRPC design [OK]

Common Mistakes:

• Building large monolithic gRPC services
• Using REST internally instead of gRPC
• Ignoring Protocol Buffers benefits