Bazel vs Maven

Which Build Tool Should You Choose?

Choosing the right build tool can make or break your team's productivity, CI/CD performance, and development experience. Two build tools dominate different ends of the spectrum: Bazel, Google's open-source version of their internal Blaze system, and Maven, the long-standing champion of Java project management.

Introduction to Bazel

Bazel is a fast, scalable, multi-language build system developed by Google. Originally created as their internal "Blaze" system, it's designed to handle massive codebases with hermetic builds, advanced caching, and distributed execution.

Overview

What is Bazel

Bazel started as Google's internal build tool called "Blaze," with development beginning in 2006. Google created Blaze as their fourth iteration of internal build systems, designed to handle the massive scale of Google3 (Google's monorepo) containing millions of lines of code across multiple languages.

Google released Bazel publicly in March 2015, entering beta status by September 2015. Bazel 1.0 arrived in October 2019 as the first stable release, with Bazel 8.0 LTS launching in December 2024 as the current long-term support version.

Hermetic and Deterministic Builds

Bazel enforces hermetic builds through sandboxing, where each build action runs in an isolated environment with only explicitly declared inputs accessible.

Connect dots with check marks

Advanced Remote Caching and Execution

Bazel implements a sophisticated remote caching system using an Action Cache (AC) that maps action hashes to action result metadata, paired with a Content-Addressable Store (CAS) for output files.

An abstract image showing several Bazel projects writing to and reading from a remote cache.

Multi-Language Monorepo Support

Bazel's Bzlmod system provides modular external dependency management, automatically resolving transitive dependencies using a dependency graph.

module(
    name = "my_project",
    version = "1.0.0",
)

# Language rules
bazel_dep(name = "rules_java", version = "7.1.0")
bazel_dep(name = "rules_python", version = "0.25.0")

# External dependencies
bazel_dep(name = "protobuf", version = "21.7", repo_name = "com_google_protobuf")
bazel_dep(name = "abseil-cpp", version = "20230125.3")
bazel_dep(name = "googletest", version = "1.14.0")

# Python toolchain
python = use_extension("@rules_python//python/extensions:python.bzl", "python")
python.toolchain(python_version = "3.11")

# Maven dependencies for Java
maven = use_extension("@rules_jvm_external//extension:maven.bzl", "maven")
maven.install(
    artifacts = [
        "com.google.guava:guava:32.1.1-jre",
        "junit:junit:4.13.2",
    ],
)
use_repo(maven, "maven")

What are the trade offs?

Let’s take a look at the advantages and disadvantages of choosing Bazel.

Advantages

Here are the advantages of using Bazel.

  1. Incremental Build Performance: Only rebuilds what has changed by analyzing dependency graphs and tracking file content changes.
  2. Advanced Caching Capabilities: Implements both local and remote caching with artifact sharing across teams and CI systems.
  3. Massive Scalability: Designed to handle codebases with 100,000+ source files and support user bases in the tens of thousands.
  4. Build Reproducibility and Correctness: Provides hermetic builds through sandboxing, providing identical outputs from identical inputs across different machines and environments.
  5. Multi-Platform and Multi-Language Support: Native support for building across Linux, macOS, and Windows with built-in rules for Java, Kotlin, Scala, C, C++, Go, Python, Rust, JavaScript, Objective-C, and bash scripts.

Disadvantages

Here are the disadvantages of using Bazel.

  1. Steep Learning Curve and Complexity: Requires learning Starlark language syntax and Bazel-specific concepts from scratch. Developers must grasp BUILD file structure, dependency declarations, and sandboxing constraints.
  2. Verbose Configuration and Setup Complexity: BUILD files require explicit declaration of all dependencies, which can become overwhelming for simple projects.
  3. Frontend Development Limitations: Particularly challenging for Node.js and JavaScript projects due to NPM package management conflicts.
  4. Resource Intensive and Memory Usage: The Bazel server process is very resource-hungry, requiring significant memory for analysis cache and coordination of thousands of RPCs.
  5. Limited IDE Integration: While JetBrains IDEs have good support through the IntelliJ plugin (1 million downloads), comprehensive IDE integration remains limited compared to native build systems.

Introduction to Maven

Maven is a mature, convention-over-configuration build tool that has dominated Java development for over 20 years. It emphasizes standardization, dependency management, and developer productivity through established patterns and extensive tooling.

Overview

What is Maven

Maven was created by Jason van Zyl in 2002 as a subproject of Apache Turbine. Maven 1.0 was released on July 13, 2004, with the major architectural overhaul coming with Maven 2.0 in October 2005, which introduced the current POM structure and repository system. Maven 3.0 followed in October 2010, bringing parallel build support and a re-worked core Project Builder while maintaining backward compatibility.

Despite being over 20 years old, Maven remains the most widely-used build tool in the Java ecosystem, serving as the foundation for countless enterprise applications and open-source projects.

Dependency Management System

Maven's sophisticated dependency resolution automatically handles transitive dependencies, using "nearest definition" rules to resolve version conflicts.

Lots of connected dots

Project Object Model (POM)

The XML-based project descriptor contains all project information and configuration through a standardized structure. Core elements include project coordinates (groupId, artifactId, version), dependencies, build configuration, and project metadata.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
         http://maven.apache.org/xsd/maven-4.0.0.xsd">
    
    <modelVersion>4.0.0</modelVersion>
    
    <!-- Project coordinates -->
    <groupId>com.example</groupId>
    <artifactId>simple-maven-app</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    
    <!-- Project information -->
    <name>Simple Maven Application</name>
    <description>A simple Maven project example</description>
    
    <!-- Properties -->
    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    
    <!-- Dependencies -->
    <dependencies>
        <!-- JUnit for testing -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>5.8.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    
    <!-- Build configuration -->
    <build>
        <plugins>
            <!-- Maven Compiler Plugin -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>11</source>
                    <target>11</target>
                </configuration>
            </plugin>
            
            <!-- Maven Surefire Plugin for running tests -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>3.0.0-M7</version>
            </plugin>
        </plugins>
    </build>
    
</project>

Plugin Architecture

Maven's extensible plugin-based architecture is built around three standardized build lifecycles: Default (validate → compile → test → package → install → deploy), Clean (pre-clean → clean → post-clean), and Site (pre-site → site → post-site → site-deploy).

Build model

What are the trade offs?

Let’s take a look at the advantages and disadvantages of choosing Maven.

Advantages

Here are the advantages of using Maven.

  1. Convention Over Configuration: Maven enforces standard directory layouts (src/main/java, src/test/java) and build processes, reducing configuration overhead and making projects instantly familiar to developers.
  2. Dependency Management: Maven automatically resolves and downloads all required dependencies and their transitive dependencies, eliminating "JAR hell" and manual library management.
  3. IDE Integration: Excellent integration with major IDEs including IntelliJ IDEA, Eclipse, NetBeans, and Visual Studio Code.
  4. Plugin Ecosystem: A vast ecosystem of mature plugins exists for code generation, testing, reporting, static analysis, deployment, and integration with other tools.
  5. Documentation and Community: Over 20 years of development has resulted in extensive official documentation, active community forums, comprehensive Stack Overflow support, and countless best practices and tutorials available online.

Disadvantages

Here are the disadvantages of using Maven.

  1. XML Verbosity and Complexity: POM files become extremely verbose for complex projects, requiring extensive XML markup for simple dependency declarations.
  2. Performance Limitations: Maven can be 2x slower than Gradle in some scenarios and up to 100x slower for large builds without build cache.
  3. Rigid Project Structure Constraints: Maven's "opinionated" approach enforces specific directory structures and build patterns that may not fit all project types.
  4. Dependency Resolution Issues: Dependency conflicts can be difficult to debug and resolve. The "nearest definition" rule sometimes selects unexpected versions, and SNAPSHOT dependencies cause repeated metadata downloads and build inconsistencies, particularly problematic in CI/CD environments.
  5. Limited Build Customization: Customizing build processes beyond standard lifecycles requires extensive plugin development or complex Ant integration.

How do Bazel and Maven compare?

Selecting between Bazel and Maven depends on your project's unique needs and your team's expertise. Comparing how they perform across essential areas will guide you toward the right choice.

Performance and Scalability

When evaluating build tools for large-scale development, performance characteristics become a critical differentiator. Both tools approach scalability from different angles, with distinct advantages depending on project size and complexity.

Bazel

Bazel excels in build performance for large projects, with companies reporting 5-10x improvements in CI build times after migration. Its fine-grained caching and parallel execution capabilities shine in monorepo environments. The tool's analysis phase, while adding initial overhead, enables sophisticated optimizations that pay dividends at scale.

Maven

Maven, while slower for large builds, provides predictable performance for standard projects without the overhead of Bazel's analysis phase. For projects under 100 modules, Maven's simplicity often outweighs Bazel's performance advantages. The tool's straightforward execution model makes build times easy to predict and debug.

Developer Experience and Learning Curve

The developer experience represents perhaps the most significant practical difference between these tools, directly impacting team productivity and adoption success.

Bazel

Bazel requires significant investment in learning Starlark, grasping BUILD files, and adapting to sandboxed builds. However, Bazel's explicit nature prevents many subtle bugs that plague Maven builds, providing long-term benefits for large teams. The initial learning curve is steep but pays dividends in build reliability.

Maven

Maven wins decisively in ease of adoption, with developers becoming productive in days rather than months. Its familiar XML configuration and extensive IDE support reduce cognitive load. The tool's conventions provide clear guidance for project structure and common tasks.

Ecosystem and Community Support

The maturity and breadth of ecosystem support often determines the practical feasibility of adopting a build tool in enterprise environments.

Bazel

Bazel's smaller but growing community focuses on large-scale challenges, with excellent support from companies like Google but limited resources for smaller teams. The Bazel Central Registry's 500+ modules pale compared to Maven Central's millions of artifacts, though quality often exceeds quantity for enterprise use cases.

Maven

Maven's 20-year history has created an unmatched ecosystem with 5,800+ plugins and extensive documentation. Finding Maven expertise is straightforward, and solutions to common problems are well-documented. The tool's widespread adoption ensures abundant community resources and third-party integrations.

Language and Platform Support

Multi-language support becomes increasingly important as organizations adopt polyglot architectures and diverse technology stacks.

Bazel

Bazel provides superior multi-language support, enabling seamless integration of Java, C++, Python, Go, and other languages in a single build. This makes it ideal for polyglot microservices or ML projects combining Python and C++. The unified build model simplifies dependency management across language boundaries.

Maven

Maven remains primarily Java-focused, requiring additional tooling for multi-language projects. Both tools support cross-platform builds, but Maven's ecosystem is deeply rooted in JVM technologies. Extensions exist for other languages, but they often feel like afterthoughts rather than first-class citizens.

Reproducibility and Correctness

Build reproducibility has become a critical requirement for enterprise development, affecting everything from debugging to compliance requirements.

Bazel

Bazel's hermetic builds guarantee reproducibility through sandboxing and explicit dependencies, critical for regulated industries or large teams. The tool's strict approach to dependency management eliminates many classes of build failures that plague other systems.

Maven

Maven's reliance on local environments and implicit dependencies can lead to "works on my machine" issues. However, Maven's flexibility allows quick workarounds for edge cases that might require significant effort to properly configure in Bazel. The tool's pragmatic approach prioritizes developer convenience over strict reproducibility.

Which tool should you pick?

Your choice between Bazel and Maven should match your team's needs, existing toolchain, and operational priorities.

Bazel is ideal for:

  1. Large-Scale Monorepos: Companies like Google, Uber (70,000+ Go files), and Stripe use Bazel to manage massive monorepos efficiently.
  2. Multi-Language Engineering Teams: Organizations building polyglot services benefit from Bazel's unified build system.
  3. High-Performance CI/CD Requirements: When CI build time directly impacts developer productivity and deployment velocity, Bazel delivers dramatic improvements.
  4. Regulated Industries Requiring Reproducibility: Financial services, healthcare, and aerospace companies like SpaceX choose Bazel for its hermetic builds.
  5. Platform Engineering Teams: Enterprise platform teams at companies like Uber, Netflix, and Dropbox invest in Bazel to serve hundreds of developers efficiently.
  6. Complex Dependency Graphs: Projects like TensorFlow and Android AOSP with intricate interdependencies benefit from Bazel's sophisticated dependency analysis and fine-grained caching, enabling efficient builds despite complexity.
  7. Google Cloud Platform Integration: Organizations heavily invested in GCP benefit from Bazel's native integration with Google's cloud infrastructure, including seamless remote execution and caching capabilities.

Maven is ideal for:

  1. Java-Centric Enterprise Applications: Spring Boot applications, traditional enterprise Java projects, and JVM-based microservices align perfectly with Maven's conventions.
  2. Small to Medium Development Teams: Teams of 2-50 developers benefit from Maven's gentle learning curve and minimal setup requirements.
  3. Rapid Prototyping and New Projects: Maven's archetype system enables project creation in minutes with sensible defaults.
  4. Open Source Java Projects: The Apache Foundation and Spring ecosystem demonstrate Maven's dominance in open source.
  5. Traditional Enterprise Environments: Banks, insurance companies, and government agencies trust Maven's stability and mature tooling.
  6. Teams Without Dedicated Build Engineers: Product-focused teams and consultancies benefit from Maven's convention-over-configuration approach.
  7. Standard Architecture Projects: REST APIs, web applications, and microservices following standard patterns align well with Maven's conventions.

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