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Backend Development for New and Existing Products

Mad Devs designs and delivers application backends for new products and existing systems. Scope can include backend features, APIs, and integrations, architecture improvements, targeted performance work, and gradual modernization.

Discuss your backend project

What needs to change
in your backend?

Choose the situation closest to yours. We can start with a defined development scope, join an existing system, investigate a known bottleneck, or assess technical risks when the right next step is still unclear.

Build a new backend

Build a new backend

Turn product requirements into business logic, data models, APIs, integrations, and a backend ready to support the first release.

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Extend or take over an existing backend

Add features, stabilize delivery, or continue work after another team leaves without assuming the system needs to be rebuilt.

Build APIs and connect systems

Build APIs and connect systems

Create or improve APIs and integrations for frontend, mobile, partners, internal systems, payments, identity, messaging, or external data.

Improve backend performance

Improve backend performance

Investigate slow endpoints, database pressure, queues, background jobs, caching, or other known bottlenecks.

Modernize a legacy backend

Modernize a legacy backend

Change the parts of the architecture that limit delivery through focused refactoring, extraction, replatforming, or replacement.

Add backend capacity

Add backend capacity

Bring individual backend engineers or a dedicated delivery team into an existing roadmap.

Backend engineering built around
the work in front of you

Backend work is organized around the product problem, current-system constraints, and who will own the result. Technologies and architecture patterns support the work rather than define the service.

Backend application development

Build the server-side product layer for a new web, mobile, or platform experience, including business logic, data models, API contracts, authentication, integrations, tests, and release preparation.

Typical situations:

  • A new product needs its first backend.
  • A frontend or mobile team needs a backend stream.
  • A product needs a new backend module or workflow.

    What you get:
  • Defined backend scope and architecture decisions.
  • Implemented business logic, data models, and APIs.
  • Integration and testing approach.
  • Documentation and release inputs.
Discuss a new backend

API development and system integrations

Design and build APIs that connect client applications, partners, and internal systems. Scope can include authentication, versioning, error handling, webhooks, integrations, and testing.

Typical situations:

  • Frontend or mobile teams need stable APIs.
  • A product needs payment, identity, or messaging integrations.
  • Internal systems need to exchange data.
  • Existing integrations are difficult to maintain.

    What you get:
  • Defined API and integration contracts.
  • Endpoints, adapters, or webhook flows.
  • Authentication and error-handling approach.
  • Tests and documentation.
Plan an API or integration

Existing backend development and ownership

Extend, stabilize, and document an existing backend without assuming it needs replacement. Work starts from the current codebase, APIs, data constraints, and delivery workflow.

Typical situations:

  • A previous vendor or key engineer has left.
  • Feature delivery has slowed in an existing codebase.
  • Documentation is incomplete.
  • Your internal team needs additional backend ownership.

    What you get:
  • Clear ownership and dependency boundaries.
  • Prioritized delivery plan.
  • Features, fixes, or stabilization work.
  • Documentation and knowledge transfer.
Discuss an existing backend

Backend modernization and architecture improvement

Improve an existing backend when architecture, dependencies, or system boundaries slow delivery or increase risk. The goal is to change only the parts that are creating the constraint.

Typical situations:

  • Modules are tightly coupled and difficult to change.
  • Legacy dependencies or runtime versions create risk.
  • Architecture no longer matches product ownership.
  • A monolith needs gradual modernization.

    What you get:
  • Clear modernization approach and priorities.
  • Refactoring, extraction, migration, or replacement where needed.
  • Compatibility and testing safeguards.
  • Updated architecture and boundary documentation.
Discuss modernization options

Backend performance and data access improvement

Investigate backend bottlenecks before deciding what needs to change. The work can cover application logic, database queries, caching, queues, background jobs, concurrency, and data-access patterns.

Typical situations:

  • API responses become slower as usage grows.
  • Database queries or indexing affect performance.
  • Background jobs compete with user requests.
  • The team is unsure whether the bottleneck is code, data, or infrastructure.

    What you get:
  • Evidence of where the bottleneck occurs.
  • Prioritized backend and data improvements.
  • Measurement approach for agreed changes.
  • Clear handoff to DevOps when the constraint is infrastructure.
Discuss a backend bottleneck

Backend application development

Build the server-side product layer for a new web, mobile, or platform experience, including business logic, data models, API contracts, authentication, integrations, tests, and release preparation.

Typical situations:

  • A new product needs its first backend.
  • A frontend or mobile team needs a backend stream.
  • A product needs a new backend module or workflow.

    What you get:
  • Defined backend scope and architecture decisions.
  • Implemented business logic, data models, and APIs.
  • Integration and testing approach.
  • Documentation and release inputs.
Discuss a new backend

API development and system integrations

Design and build APIs that connect client applications, partners, and internal systems. Scope can include authentication, versioning, error handling, webhooks, integrations, and testing.

Typical situations:

  • Frontend or mobile teams need stable APIs.
  • A product needs payment, identity, or messaging integrations.
  • Internal systems need to exchange data.
  • Existing integrations are difficult to maintain.

    What you get:
  • Defined API and integration contracts.
  • Endpoints, adapters, or webhook flows.
  • Authentication and error-handling approach.
  • Tests and documentation.
Plan an API or integration

Existing backend development and ownership

Extend, stabilize, and document an existing backend without assuming it needs replacement. Work starts from the current codebase, APIs, data constraints, and delivery workflow.

Typical situations:

  • A previous vendor or key engineer has left.
  • Feature delivery has slowed in an existing codebase.
  • Documentation is incomplete.
  • Your internal team needs additional backend ownership.

    What you get:
  • Clear ownership and dependency boundaries.
  • Prioritized delivery plan.
  • Features, fixes, or stabilization work.
  • Documentation and knowledge transfer.
Discuss an existing backend

Backend modernization and architecture improvement

Improve an existing backend when architecture, dependencies, or system boundaries slow delivery or increase risk. The goal is to change only the parts that are creating the constraint.

Typical situations:

  • Modules are tightly coupled and difficult to change.
  • Legacy dependencies or runtime versions create risk.
  • Architecture no longer matches product ownership.
  • A monolith needs gradual modernization.

    What you get:
  • Clear modernization approach and priorities.
  • Refactoring, extraction, migration, or replacement where needed.
  • Compatibility and testing safeguards.
  • Updated architecture and boundary documentation.
Discuss modernization options

Backend performance and data access improvement

Investigate backend bottlenecks before deciding what needs to change. The work can cover application logic, database queries, caching, queues, background jobs, concurrency, and data-access patterns.

Typical situations:

  • API responses become slower as usage grows.
  • Database queries or indexing affect performance.
  • Background jobs compete with user requests.
  • The team is unsure whether the bottleneck is code, data, or infrastructure.

    What you get:
  • Evidence of where the bottleneck occurs.
  • Prioritized backend and data improvements.
  • Measurement approach for agreed changes.
  • Clear handoff to DevOps when the constraint is infrastructure.
Discuss a backend bottleneck
Modernize without defaulting
to a rewrite

The right change depends on what is actually limiting delivery. A full rewrite or move to microservices should be an outcome of that assessment, not the starting assumption.

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Refactor

Refactor when the overall architecture still works, but code structure, dependencies, or individual modules make changes risky or slow. Improve the internal structure while keeping existing behavior stable.

Extract

Extract

Extract a domain capability when it needs clearer ownership, an independent delivery boundary, or less coupling with the rest of the system. Keep the separation focused on a specific business or technical need.

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Replatform

Replatform when the main constraint comes from the runtime, platform dependency, or unsupported foundation rather than the product architecture itself. Change the underlying environment while keeping the scope controlled.

Replace or rebuild a bounded area

Replace or rebuild a bounded area

Replace a specific component or rebuild a contained capability when incremental changes create more cost or risk than a focused replacement. Keep the scope limited and preserve stable parts of the system where possible.

Take over an inherited backend

A backend built by another team does not always need a full audit or rewrite. If the system is healthy and documented, we can move directly into onboarding and delivery. When key parts are unclear, we first identify the risks that could affect ownership, releases, or further development.

Understand the system

Understand the system

Review the relevant codebase, services, APIs, data dependencies, and current delivery workflow. The goal is to understand how the system works today and what context is needed to continue development safely.

Map unknown risks

Map unknown risks

Identify gaps in documentation, unclear dependencies, release risks, or areas where system behavior is not fully understood. A targeted technical assessment can be added when those unknowns materially affect delivery.

Define ownership

Define ownership

Agree which parts of the backend Mad Devs owns, what remains with the internal team, and how technical decisions, access, documentation, and communication will be handled.

Continue delivery

Continue delivery

Move into the next feature, stabilization, or modernization step with agreed priorities and ownership. Keep the relevant technical context documented as the work continues.

How we deliver
backend development

The process adapts to the system, scope, and level of risk. A new backend may require architecture and interface decisions upfront, while an existing system can often start with focused onboarding and a clearly defined delivery scope.

We clarify what the backend needs to support, who or what depends on it, and which constraints matter for delivery. For an existing system, we also review the relevant codebase and current behavior without turning onboarding into an unnecessary full audit.

Define the backend delivery scope

Technologies we use

Python

Python

High-level, interactive, and object-oriented programming language.

Go

Go

Statically typed language that is similar to C but with garbage collection and memory safety.

Node

Node.js

JavaScript

JavaScript

TypeScript

TypeScript

PHP

PHP

Ruby

Ruby

Redis

Redis

Mongo

Mongo

Sentry

Sentry

Elastic APM

Elastic APM

Loki

Loki

ELK

ELK

Prometheus

Prometheus

Gitlab CI

Gitlab CI

Clickhouse

Clickhouse

MySQL

MySQL

Postgres

Postgres

Stripe

Stripe

Twilio

Twilio

Google APIs

Google APIs

sendgrid

SendGrid

Datadog

Datadog

Firebase

Firebase

Neo4j

Neo4j

Flask

Flask

Pytest

Pytest

Airflow

Airflow

Graphana

Graphana

Discuss the backend problem you need to solve

Share what is changing, what exists today and where the uncertainty is. A conversation can start with a defined build, API, integration, bottleneck, modernization step, takeover or capacity need.

Case studies

B 2 B

The growth of Clutch.co

BYOD

Sir John Monash Centre

See more case studies

Backend engineering notes

Concept of Unit-Tests Writing in Golang.

Concept of Unit-Tests Writing in Golang

Unit tests, in most cases, are associated with a lot of wasted time. A test is an imitation of a user browsing the page. Finding errors during the testing stage improves the user experience. Duh. Testing automatically catches bugs and thus builds the business's credibility. However, I do agree that writing tests is a long and, in most cases, boring process. Since usually, I am usually the one who writes almost all tests for my colleagues, I can tell that writing tests is more complicated than writing code. Writing code is straightforward since you always see the final result you aim to achieve. However, writing tests involve designing all possible scenarios, analyzing data, and uncovering non-obvious use cases. Ideally, you want to test everything, even the smallest details, immediately. Even after doing it for years, to this day, I still frequently get confused by loads of ideas and cannot choose the needed scenario. So, I have developed some concepts for test writing. They facilitate the entire procedure and prevent me (and possibly you) from missing or forgetting something important. I believe they might be useful for you, too.

Introduction to the World of Application Design.

Software Architecture 101 – Introduction to the World of Application Design

Hello, everyone!Today, I would like to introduce you to the world of application design.Designing applications can be called a multidisciplinary task, and it includes:

Effective Refactoring of a Heavy Database Interface.

Effective Refactoring of a Heavy Database Interface

This story is about pain, agony, and denial of ready-made solutions. It is also about changes that improve the code's readability and help the development team stay happy. The object of this post is an interface that helps a program communicate with a database.Disclaimer: If we would use various ORMs such as Gorm in this project, most probably we would not face this issue, yet, we decided to write our implementation, so this created the issue and therefore this post.

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FAQs

Yes. Work can begin with direct onboarding into a healthy, sufficiently documented system, then focus on the agreed feature, integration, stabilisation or modernization scope. If key behaviour, documentation or production risk is unknown, a targeted assessment may be the safer first step. The aim is to understand enough to deliver safely, not to turn every inherited system into a rewrite project.

Yes. Start by agreeing the relevant repositories, interfaces, deployment context, current priorities and ownership boundaries. A well-understood system can move quickly into delivery. Where there are material unknowns, map the specific release, data or dependency risks first and agree what needs documentation or remediation. Takeover depth should match actual uncertainty.

Yes. A backend delivery stream can work alongside your frontend or mobile team. The shared work is to agree API contracts, authentication, error behaviour, test responsibilities and release coordination early enough that teams can progress independently. If you need the client application delivered as well, Mad Devs can discuss adjacent frontend or mobile scope separately.

Yes. The work can cover internal, partner and public APIs, plus integrations with external providers or internal business systems. Scope is defined around consumers, ownership, authentication, validation, versioning, failure handling and documentation. The appropriate interface style, such as REST or GraphQL, follows the product and integration constraints rather than a fixed preference.

Yes, where the bottleneck is in backend logic, data access, caching, queues, jobs, concurrency, or architecture. Investigation should establish the limiting path before a solution or target gain is promised. If evidence points to infrastructure, deployment, cluster capacity, or cloud configuration, the work should be coordinated with the appropriate DevOps or Cloud scope.

Not necessarily. Microservices add operational and coordination costs as well as potential delivery benefits. The decision should follow domain and ownership boundaries, deployment needs, product scale, operational cost and the constraints of the current system. A modular monolith, targeted extraction or a bounded refactor may be the better next step.

Often, yes. Useful options include refactoring a constrained module, extracting a domain capability, replatforming an unsupported foundation, replacing a high-risk component, or rebuilding a bounded area. The right approach depends on the current system and the business change it must support. A full rewrite is considered only when its risk and cost are justified by the alternatives.

An estimate is shaped by the definition and condition of the scope: existing-code documentation, architecture and data complexity, integrations, migration needs, expected traffic, testing/security requirements, release constraints and delivery model. A known bounded task can be scoped directly. A high-uncertainty inherited system may need a focused technical assessment before a reliable delivery plan is possible.