Gigabytes in your JVM. Nothing for the GC to scan.

NoHeapDB db = new NoHeapDB();

// A 1 GB in-memory store; it adds chunks as it grows
db.createStore("cache", DataStore.Storage.IN_MEMORY, 1024);

db.putString("cache", "user:42", "Alice");
db.putInteger("cache", "visits:42", 17);

String name = db.getString("cache", "user:42");     // "Alice"
Integer visits = db.getInteger("cache", "visits:42"); // 17

db.remove("cache", "visits:42");

for (Iterator<String> keys = db.keys("cache"); keys.hasNext(); ) {
    System.out.println(keys.next());
}

db.deleteStore("cache");   // frees all of its memory now

// A view of the stored bytes: nothing is copied onto the heap
RecordView view = db.getView("cache", "user:42");

int length = view.length();
byte first = view.get(0);

// read() hands your code a read-only ByteBuffer, then checks
// the record's version stamp again before returning
boolean startsWithA = view.read(bytes -> bytes.get(0) == 'A');

db.remove("cache", "user:42");
view.get(0);   // throws StaleViewException: the record is gone

NoHeapDB db = new NoHeapDB("/data/myapp/offheap");  // default: ~/JavaOffHeap

db.createStore("orders", DataStore.Storage.PERSISTED, 1024);
db.putString("orders", "order:1001", "{\"total\": 129.95}");
db.closeStore("orders");    // flush and unmap; the files stay

// Later, or in a new JVM: the same call reopens the files
db.createStore("orders", DataStore.Storage.PERSISTED, 1024);
db.getString("orders", "order:1001");

// NoHeapDB reports its own memory use
long bytes  = db.getAllocatedBytes("orders");
long mapped = NoHeapDB.getTotalMappedBytes();

HybridDB db = new HybridDB();

NoHeapCollection employees = db.createCollection("employees");
employees.createIndex("department");   // O(1) lookups by department

String id = employees.insert(
    Document.create()
        .set("name", "Alice Martin")
        .set("department", "Engineering")
        .set("salary", 135000));

List<Document> engineers = employees.find("department", "Engineering");

Document alice = employees.findById(id);
alice.set("salary", 142000);
employees.update(alice);

db.dropCollection("employees");

HybridDB db = new HybridDB();
NoHeapGraph graph = db.createGraph("accounts");

String alice = graph.addNode("Person",  Map.of("name", "Alice"));
String bob   = graph.addNode("Person",  Map.of("name", "Bob"));
String acct  = graph.addNode("Account", Map.of("iban", "DE89 3704"));

graph.addEdge(alice, acct, "OWNS", Map.of());
graph.addEdge(bob,   acct, "SENT_TO", Map.of("amount", "9500"));

List<Node> neighbors = graph.getNeighbors(alice);
List<Node> reachable = graph.bfs(alice);
List<Node> path      = graph.shortestPath(bob, alice);

db.dropGraph("accounts");