diff --git a/api/server/pom.xml b/api/server/pom.xml
index 26ce369..fab4130 100644
--- a/api/server/pom.xml
+++ b/api/server/pom.xml
@@ -1,111 +1,116 @@
 <?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>
 
     <groupId>org.softwareheritage.graph</groupId>
     <artifactId>graph</artifactId>
     <version>1.0-ALPHA</version>
 
     <name>graph</name>
     <url>https://www.softwareheritage.org/</url>
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
     </properties>
 
     <dependencies>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <version>4.11</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>io.javalin</groupId>
             <artifactId>javalin</artifactId>
             <version>2.8.0</version>
         </dependency>
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-simple</artifactId>
             <version>1.7.26</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
             <version>2.9.8</version>
         </dependency>
+        <dependency>
+            <groupId>it.unimi.dsi</groupId>
+            <artifactId>webgraph</artifactId>
+            <version>3.6.1</version>
+        </dependency>
     </dependencies>
 
     <build>
         <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
             <plugins>
                 <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
                 <plugin>
                     <artifactId>maven-clean-plugin</artifactId>
                     <version>3.1.0</version>
                 </plugin>
                 <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
                 <plugin>
                     <artifactId>maven-resources-plugin</artifactId>
                     <version>3.0.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-compiler-plugin</artifactId>
                     <version>3.8.0</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-surefire-plugin</artifactId>
                     <version>2.22.1</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-jar-plugin</artifactId>
                     <version>3.0.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-install-plugin</artifactId>
                     <version>2.5.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-deploy-plugin</artifactId>
                     <version>2.8.2</version>
                 </plugin>
                 <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
                 <plugin>
                     <artifactId>maven-site-plugin</artifactId>
                     <version>3.7.1</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-project-info-reports-plugin</artifactId>
                     <version>3.0.0</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-assembly-plugin</artifactId>
                     <configuration>
                         <archive>
                             <manifest>
                                 <mainClass>org.softwareheritage.graph.App</mainClass>
                             </manifest>
                         </archive>
                         <descriptorRefs>
                             <descriptorRef>jar-with-dependencies</descriptorRef>
                         </descriptorRefs>
                     </configuration>
                     <executions>
                         <execution>
                             <id>make-assembly</id> <!-- this is used for inheritance merges -->
                             <phase>package</phase> <!-- bind to the packaging phase -->
                             <goals>
                                 <goal>single</goal>
                             </goals>
                         </execution>
                     </executions>
                 </plugin>
             </plugins>
         </pluginManagement>
     </build>
 </project>
diff --git a/api/server/src/main/java/org/softwareheritage/graph/App.java b/api/server/src/main/java/org/softwareheritage/graph/App.java
index b07b18c..ffad3ad 100644
--- a/api/server/src/main/java/org/softwareheritage/graph/App.java
+++ b/api/server/src/main/java/org/softwareheritage/graph/App.java
@@ -1,18 +1,18 @@
 package org.softwareheritage.graph;
 
 import io.javalin.Javalin;
 
 import org.softwareheritage.graph.GraphAPI;
 
 public class App
 {
     public static void main(String[] args)
     {
-        GraphAPI graph = new GraphAPI();
+        GraphAPI graph = new GraphAPI("/path/to/graph");
 
         Javalin app = Javalin.create().start(5010);
         app.get("/nb_nodes", ctx -> {
             ctx.json(graph.nbNodes());
         });
     }
 }
diff --git a/api/server/src/main/java/org/softwareheritage/graph/GraphAPI.java b/api/server/src/main/java/org/softwareheritage/graph/GraphAPI.java
index 9e68bd9..c16ff19 100644
--- a/api/server/src/main/java/org/softwareheritage/graph/GraphAPI.java
+++ b/api/server/src/main/java/org/softwareheritage/graph/GraphAPI.java
@@ -1,9 +1,27 @@
 package org.softwareheritage.graph;
 
+import java.io.IOException;
+
+import it.unimi.dsi.webgraph.BVGraph;
+
 public class GraphAPI
 {
+    String graphName;
+    BVGraph graph;
+
+    public GraphAPI(String graphName)
+    {
+        this.graphName = graphName;
+        try {
+            this.graph = BVGraph.load(graphName);
+        }
+        catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     public int nbNodes()
     {
-        return 42;
+        return graph.numNodes();
     }
 }