10. Monolith vs Microservices

Question 1

what is a monolithic enterprise application architecture

Answer 1

enterprise application built as a single unit with a single logical executable

Question 2

main parts of a Monolithic Enterprise Application Architecture

Answer 2

1. Client-side UI
2. database
3. server-side application that handles : HTTP logic, executes business logic, retrieve and update data from database, select and populate HTML, etc –> usually deployed as a single package (monolith/monolithic application)

Question 3

characteristics of a monolith

Answer 3

• has a single code base implementing all functions needed for various business processes -> may become large and complex, difficult to understand and maintain
• typically developed in one programming language on one platform: easier for different parts of the application to be compatible, less flexible for the choices of technologies, less suitable for heterogeneous environments
• deployment is all or none: due to dependencies
• scale entire application, not just a function

Question 4

what does single unit/package mean?

Answer 4

• does not mean the monolith only has one function, module or database.
• can have multiple module, connected to multiple dbs
• modules are bundled/packaged together –> maybe too big/complex and interface may be ad-hoc and not standardised enough to be called service interfaces

Question 5

whats a microservice

Answer 5

• a single unit that implements only one or few (instead of many) functionality(ies)
• can be invoked by other applications/microservices over the network in a standard interface that is independent of programming languages and platforms

Question 6

why are microservices “loosely coupled”

Answer 6

• implemented in a programming language of its own
• can be deployed and run on a platform of its own
• has its own datastore
• scaled independently
• implementation can be changed independently (interface for invocation remains the same)

Question 7

what is the purpose of an adaptor /wrapper

Answer 7

provide easier interfaces to an app so that it’d be easier for other apps to use the functionalities of this app

Question 8

whats an adaptor/wrapper service

Answer 8

interfaces that are language-/platform-agnostic and can be used by other apps across networks

Question 9

adaptor vs wrapper

Answer 9

“adapters” may often be used when they are provided by the third-party software vendors and have more complex internals; “wrappers” may often be used when they are built by our organization for third-party software and have simpler internals

Question 10

types of microservices (2)

Answer 10

atomic/simple
composite/complex

Question 11

what is an atomic (micro)service

Answer 11

• provides functionality related to one kind of entity of a business concern
• implementation is independent of others
• self-contained, without depending on monolith / other microservices
• may depend on others as a “wrapper” to expose some functionality in a monolith or external API
• may not directly communicate to other microservices BUT may send reply data

Question 12

what is a composite (micro)service

Answer 12

• provides functionality related to more than 1 entity
• functionality provided consists of a set/sequence of activities (including direct/indirect communication with others) for a business process, which are dependent on others
• microservice may depend on other (micro)services but should not directly depend on a monolith
• service may depend on monolith and (micro)services but not recommended (increases coupling, harder to deploy/scale independently)
• needs to know interfaces of all others it communicates with

Question 13

who do composite microservices communicate with

Answer 13

• can directly communicate with another composite (micro)service and atomic (micro)service
• CANNOT communicate with IT systems/monoliths