To resolve ambiguity in autowiring of beans, you can use the @Qualifier annotation to specify the bean name or qualifier explicitly. This approach ensures that the correct bean is injected. The @Primary annotation designates a primary bean, which can also help resolve ambiguity. The other options don't directly address ambiguity resolution.

Option 3 is the recommended approach. Tools like WireMock and MockServer allow you to create mock endpoints for external APIs, ensuring that actual API calls are not made during testing.

In Spring Security, the AuthenticationProvider is responsible for creating a user Authentication object from an HttpServletRequest. The AuthenticationProvider is a core component in Spring Security that takes care of authenticating users. It verifies user credentials and loads user-specific details, ultimately creating the Authentication object that represents the authenticated user.

In Spring Boot, you can use the ${env} placeholder in the application properties file to resolve property values from environment variables. This is useful for configuring your Spring Boot application dynamically based on the environment it runs in, such as setting database connection parameters or API keys from environment variables.

The @SpringBootApplication annotation is used to mark the main class of a Spring Boot application. It combines several other annotations, including @Configuration, @ComponentScan, and @EnableAutoConfiguration, making it the entry point for a Spring Boot application. The other options, such as @MainClass and @EntryPoint, are not standard annotations used for this purpose.

In a read-heavy scenario, using a caching mechanism like Redis can significantly improve performance by reducing the load on the database server. By caching frequently accessed data, you can serve read requests from the cache, reducing the database load. Database sharding is more relevant for write-heavy workloads, and increasing write capacity and implementing asynchronous processing are not specific to optimizing read-heavy workloads.

To ensure optimal performance and maintainability when interacting with multiple databases in a Spring Boot application, using dynamic data source routing with a common connection pool configuration is recommended. This approach allows for efficient database interactions, as requests are routed to the appropriate data source based on the context. It also simplifies maintenance by centralizing the connection pool configuration. Configuring separate data sources for each database can lead to complexity, and a single global connection pool may not provide isolation for each database. Programmatically routing requests adds unnecessary complexity.

To configure a JWT token store in a Spring Boot application, you need to define a JwtTokenStore bean in the configuration class. This store is responsible for managing and storing JWT tokens, which are commonly used for authentication and authorization in web applications. The other options are not related to configuring a JWT token store.

The JdbcTemplate class in Spring Boot is used for low-level JDBC operations and offers more control over SQL queries and data access compared to JPA, which is an Object-Relational Mapping (ORM) tool. JdbcTemplate is particularly useful when you need precise control over your SQL queries and want to work with plain SQL. JPA, on the other hand, allows you to work with Java objects and abstracts away the underlying database operations.

To implement password hashing in Spring Security, you should use the PasswordEncoder interface and configure it in the security configuration. This ensures that passwords are securely hashed before being stored in the database and compared during authentication. The other options do not provide a standard or recommended approach for password hashing in Spring Security.