Question 1

How would you design a rate limiting system for an API, and what algorithms are commonly used?

Accepted Answer

Rate limiting controls how many requests a client can make to an API within a given time period. It protects backend services from being overwhelmed, ensures fair resource distribution among clients, and defends against abuse and denial-of-service attacks. Designing an effective rate limiting system requires choosing the right algorithm, deciding where to enforce limits, and handling edge cases gracefully.

The token bucket algorithm is one of the most widely used approaches. Each client has a bucket that holds tokens. Tokens are added at a fixed rate, say 10 tokens per second. Each request

Question 2

Explain the circuit breaker pattern and how it prevents cascading failures in distributed systems.

Accepted Answer

The circuit breaker pattern prevents a failing service from causing cascading failures across a distributed system. It works analogously to an electrical circuit breaker: when it detects that a downstream service is failing, it stops sending requests to that service, allowing it to recover while protecting the calling service from hanging on timeout after timeout.

A circuit breaker has three states. In the closed state, requests flow through normally. The circuit breaker monitors each call and tracks failures. When the failure rate exceeds a configured threshold, such as 50 percent of reque

Question 3

How do you determine the right service boundaries when decomposing a monolith into microservices?

Accepted Answer

Determining the right service boundaries is the most critical decision in microservices architecture because poorly drawn boundaries create a distributed monolith that has all the complexity of microservices with none of the benefits. Domain-Driven Design provides the most reliable framework for this decomposition.

The starting point is identifying bounded contexts within the business domain. A bounded context is a logical boundary where a particular domain model applies consistently. In an e-commerce system, the order management context, inventory context, payment context, and shipping con

Question 4

What are the main patterns for inter-service communication in microservices, and how do you choose between them?

Accepted Answer

Inter-service communication is the connective tissue of a microservices architecture. The choice of communication pattern significantly affects system reliability, performance, and coupling between services. There are two broad categories: synchronous request-response and asynchronous messaging.

Synchronous communication means the calling service sends a request and waits for a response. REST over HTTP is the most common implementation, offering simplicity, broad tooling support, and human-readable payloads. gRPC provides higher performance through binary Protocol Buffer serialization, HTTP

Question 5

What is the difference between a data lake and a data warehouse, and when would you recommend each?

Accepted Answer

Data lakes and data warehouses serve different purposes in an organization's data strategy, and understanding when to use each is fundamental for a solutions architect designing data architectures.

A data warehouse is a structured, optimized store for analytical queries. Data is cleaned, transformed, and loaded into a predefined schema before it enters the warehouse. This schema-on-write approach means queries are fast because the data is already organized for the analytical patterns the warehouse supports. Data warehouses use columnar storage formats that excel at aggregations across milli

Question 6

Explain the differences between OLTP and OLAP systems and how they influence database architecture decisions.

Accepted Answer

OLTP and OLAP represent two fundamentally different data access patterns that require different architectural approaches. Understanding these patterns is essential for making the right database and infrastructure choices.

Online Transaction Processing systems handle the day-to-day operational workload of an application. They process high volumes of short, atomic transactions like creating orders, updating inventory, and processing payments. OLTP queries typically access a small number of rows at a time using primary key lookups or indexed queries. The data model is highly normalized to mini

Question 7

What is the Zero Trust security model, and how does it change the way you design network and application security?

Accepted Answer

Zero Trust is a security model based on the principle of never trust, always verify. It fundamentally changes architectural design by eliminating the concept of a trusted internal network. In traditional perimeter-based security, resources inside the corporate network are trusted and those outside are not. Zero Trust assumes that threats exist both inside and outside the network and that every request must be authenticated, authorized, and encrypted regardless of its origin.

The core principles of Zero Trust include verifying explicitly by always authenticating and authorizing based on all

Question 8

How do you design an authentication and authorization strategy for a microservices-based application?

Accepted Answer

Authentication verifies who you are; authorization determines what you can do. In a microservices architecture, both must be designed carefully because the distributed nature creates unique challenges around token propagation, service-to-service trust, and consistent policy enforcement.

For user authentication, I implement OAuth 2.0 with OpenID Connect through a centralized identity provider such as Auth0, Okta, AWS Cognito, or Keycloak. The identity provider handles user registration, login, multi-factor authentication, and social login integrations. Upon successful authentication, it issu

Question 9

What are the six common migration strategies, often called the six Rs, and when would you recommend each one?

Accepted Answer

The six Rs provide a framework for categorizing how each application or workload should be moved to the cloud. Choosing the right strategy depends on the application's architecture, business value, technical constraints, and the organization's timeline and budget.

Rehost, commonly called lift-and-shift, moves the application to the cloud with minimal or no changes. The application runs on cloud infrastructure but does not take advantage of cloud-native features. This is the fastest migration path and works well for applications with an urgent data center exit deadline or for applications th

Question 10

What is the difference between lift-and-shift and refactoring, and how do you decide which approach to use for a given application?

Accepted Answer

Lift-and-shift and refactoring represent opposite ends of the migration effort spectrum, and choosing between them involves evaluating trade-offs between speed, cost, risk, and long-term value.

Lift-and-shift migrates an application to cloud infrastructure with minimal changes. A virtual machine running on-premises is replicated as a cloud VM. The same operating system, middleware, and application code run in the cloud. The primary benefit is speed. A lift-and-shift migration can often be completed in days or weeks rather than months. The risk is low because the application is unchanged and

Solutions Architect

Topics

Advanced System Design

Microservices Architecture

Data Architecture & Patterns

Security Architecture

Migration & Modernization Planning

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