Spring Boot API

The canonical IAM solution for Spring Boot: Spring Security's OAuth2/OIDC support connects directly to Keycloak realms for SSO, RBAC, and token-based API security. Self-hosted and free, at the cost of running and maintaining the Keycloak server yourself.

A managed alternative to Keycloak with the same enterprise IAM feature set (SSO, SAML, OIDC, MFA) but zero operational overhead, worth it if you'd rather not run an identity server at all.

A developer-friendly hosted auth platform with pre-built sign-in UI, a lighter-weight option than Keycloak or Auth0 if the app needs straightforward user accounts rather than enterprise SSO/LDAP federation.

A transactional email API for account verification, password resets, and notification emails. Resend's REST API is called directly from a Spring Boot service class, since Resend has no dedicated Java SDK. Free tier for getting started.

The established high-volume choice, with dedicated IP addresses and deliverability tooling for apps sending at serious scale. No permanent free plan (a 60-day trial, then paid tiers), so it earns its slot when volume and deliverability matter more than upfront cost.

An all-in-one platform combining the transactional email API with marketing campaigns, a built-in CRM, and SMS from the same dashboard. A permanent free tier of 300 emails a day with no card required makes it an easy starting pick for an early-stage app.

Adds subscription billing, one-time checkout, and invoicing via Stripe's Java SDK, with webhook verification and charge creation kept server-side. The stack works fully without it; add this once whatever consumes this API is ready to charge for something.

S3-compatible object storage with no egress fees, so serving uploads, images, and exports costs only for storage and operations. Spring Boot uses the AWS SDK for Java v2 (S3Client and S3Presigner) with an endpoint override, or Spring Cloud AWS's S3 module, and the keys stay in configuration or the environment. The 10 GB free tier covers an early product.

The reference object store and the API the others copy, with the most storage classes, regional controls, and lifecycle rules. Spring Boot uses the AWS SDK for Java v2 (S3Client and S3Presigner) with an endpoint override, or Spring Cloud AWS's S3 module, and the keys stay in configuration or the environment. It fits best when the rest of the app already runs on AWS, though data transfer out is billed.

An S3-compatible store at roughly a third of S3 Standard's storage price, a fit for backups and large media libraries. Spring Boot uses the AWS SDK for Java v2 (S3Client and S3Presigner) with an endpoint override, or Spring Cloud AWS's S3 module, and the keys stay in configuration or the environment. Egress is free up to three times the stored data, and a CDN in front of a public bucket covers heavier delivery.

Spring Boot auto-configures Redis through spring-boot-starter-data-redis with the Lettuce client, and Spring's cache abstraction then uses it for every @Cacheable method, so caching a service call is one annotation with a TTL set in configuration. RedisTemplate covers counters and rate limits by hand. PostgreSQL already holds hot rows in memory, so add Redis when the same reads repeat often enough to show in latency or database load.

Spring's own @Async runs a method on a background thread inside the same JVM, which suits small jobs but loses them on a restart and cannot share work across instances. For jobs that must not be lost, spring-boot-starter-amqp connects the API to RabbitMQ: an endpoint publishes a message with RabbitTemplate, a @RabbitListener method consumes it with acknowledgements and retries, and failures can go to a dead-letter queue. RabbitMQ is a separate server, run as a container next to the API or as a managed instance.

Runs the test suite and triggers deployments on every push, directly from the same GitHub repo the code already lives in, with no separate CI service to configure.

GitLab's built-in CI/CD system, configured via .gitlab-ci.yml in the repository, the natural pick if the project's code lives on GitLab (self-hosted or gitlab.com) rather than GitHub, with the same YAML-pipeline model as GitHub Actions.

Free, open source, and run on your own server instead of a hosted service, the long-standing pipeline server in Java enterprises. A Jenkinsfile in the repository runs the Maven or Gradle build and the JUnit tests, which Jenkins charts as a trend across builds, and then triggers the deployment. It works with any Git host, including a corporate one with no pipelines of its own, and keeps code and credentials inside the network. The trade is upkeep: you run the Jenkins server and its plugins, and the build agent needs a JDK that matches the project's Java version.

Packages the Spring Boot API into a container image for consistent local development and deployment, independent of the hosting platform chosen above.

Error tracking and performance monitoring with Sentry's Java SDK, wired into Spring Boot's exception handling. Open-source with a self-hosted path, alongside its own managed cloud.

A broader observability platform covering APM, infrastructure metrics, and log management in one dashboard, useful once a team is already running other services worth monitoring alongside this API. Managed-only, with pricing that scales by host and usage rather than Sentry's per-error volume.