diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/SpringBootCompositeKeyApplication.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/SpringBootCompositeKeyApplication.java
new file mode 100644
index 0000000000..e9f8eab1dd
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/SpringBootCompositeKeyApplication.java
@@ -0,0 +1,15 @@
+package com.baeldung.boot.composite.key;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.PropertySource;
+import org.springframework.data.mongodb.repository.config.EnableMongoRepositories;
+
+@SpringBootApplication
+@PropertySource("classpath:boot.composite.key/app.properties")
+@EnableMongoRepositories(basePackages = { "com.baeldung.boot.composite.key" })
+public class SpringBootCompositeKeyApplication {
+    public static void main(String... args) {
+        SpringApplication.run(SpringBootCompositeKeyApplication.class, args);
+    }
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/CustomerRepository.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/CustomerRepository.java
new file mode 100644
index 0000000000..6953a21ddd
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/CustomerRepository.java
@@ -0,0 +1,12 @@
+package com.baeldung.boot.composite.key.dao;
+
+import java.util.Optional;
+
+import org.springframework.data.mongodb.repository.MongoRepository;
+
+import com.baeldung.boot.composite.key.data.Customer;
+
+public interface CustomerRepository extends MongoRepository<Customer, String> {
+
+    Optional<Customer> findByStoreIdAndNumber(Long storeId, Long number);
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/SaleRepository.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/SaleRepository.java
new file mode 100644
index 0000000000..3caa33d465
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/SaleRepository.java
@@ -0,0 +1,12 @@
+package com.baeldung.boot.composite.key.dao;
+
+import java.util.Optional;
+
+import org.springframework.data.mongodb.repository.MongoRepository;
+
+import com.baeldung.boot.composite.key.data.Sale;
+import com.baeldung.boot.composite.key.data.TicketId;
+
+public interface SaleRepository extends MongoRepository<Sale, String> {
+    Optional<Sale> findByTicketId(TicketId ticketId);
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/TicketRepository.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/TicketRepository.java
new file mode 100644
index 0000000000..b02ea461d2
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/dao/TicketRepository.java
@@ -0,0 +1,10 @@
+package com.baeldung.boot.composite.key.dao;
+
+import org.springframework.data.mongodb.repository.MongoRepository;
+
+import com.baeldung.boot.composite.key.data.Ticket;
+import com.baeldung.boot.composite.key.data.TicketId;
+
+public interface TicketRepository extends MongoRepository<Ticket, TicketId> {
+
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Customer.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Customer.java
new file mode 100644
index 0000000000..d4bb1ef40c
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Customer.java
@@ -0,0 +1,49 @@
+package com.baeldung.boot.composite.key.data;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.index.CompoundIndex;
+import org.springframework.data.mongodb.core.mapping.Document;
+
+@Document
+@CompoundIndex(name = "customer_idx", def = "{ 'storeId': 1, 'number': 1 }", unique = true)
+public class Customer {
+    @Id
+    private String id;
+
+    private Long storeId;
+    private Long number;
+
+    private String name;
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public Long getStoreId() {
+        return storeId;
+    }
+
+    public void setStoreId(Long storeId) {
+        this.storeId = storeId;
+    }
+
+    public Long getNumber() {
+        return number;
+    }
+
+    public void setNumber(Long number) {
+        this.number = number;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Sale.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Sale.java
new file mode 100644
index 0000000000..a81c91674c
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Sale.java
@@ -0,0 +1,38 @@
+package com.baeldung.boot.composite.key.data;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.index.CompoundIndex;
+import org.springframework.data.mongodb.core.mapping.Document;
+
+@Document
+@CompoundIndex(name = "sale_idx", def = "{ 'ticketId': 1 }", unique = true)
+public class Sale {
+    @Id
+    private String id;
+
+    private TicketId ticketId;
+    private Double value;
+
+    public String getId() {
+        return id;
+    }
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public TicketId getTicketId() {
+        return ticketId;
+    }
+
+    public void setTicketId(TicketId ticketId) {
+        this.ticketId = ticketId;
+    }
+
+    public Double getValue() {
+        return value;
+    }
+
+    public void setValue(Double value) {
+        this.value = value;
+    }
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Ticket.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Ticket.java
new file mode 100644
index 0000000000..7a8ebe1ab3
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/Ticket.java
@@ -0,0 +1,31 @@
+package com.baeldung.boot.composite.key.data;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.mapping.Document;
+
+@Document
+public class Ticket {
+    @Id
+    private TicketId id;
+
+    private String event;
+
+    public Ticket() {
+    }
+
+    public TicketId getId() {
+        return id;
+    }
+
+    public void setId(TicketId id) {
+        this.id = id;
+    }
+
+    public String getEvent() {
+        return event;
+    }
+
+    public void setEvent(String event) {
+        this.event = event;
+    }
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/TicketId.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/TicketId.java
new file mode 100644
index 0000000000..76fbf81391
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/data/TicketId.java
@@ -0,0 +1,56 @@
+package com.baeldung.boot.composite.key.data;
+
+public class TicketId {
+    private String venue;
+    private String date;
+
+    public TicketId() {
+    }
+
+    public String getVenue() {
+        return venue;
+    }
+
+    public void setVenue(String venue) {
+        this.venue = venue;
+    }
+
+    public String getDate() {
+        return date;
+    }
+
+    public void setDate(String date) {
+        this.date = date;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((date == null) ? 0 : date.hashCode());
+        result = prime * result + ((venue == null) ? 0 : venue.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        TicketId other = (TicketId) obj;
+        if (date == null) {
+            if (other.date != null)
+                return false;
+        } else if (!date.equals(other.date))
+            return false;
+        if (venue == null) {
+            if (other.venue != null)
+                return false;
+        } else if (!venue.equals(other.venue))
+            return false;
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/service/CustomerService.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/service/CustomerService.java
new file mode 100644
index 0000000000..476209bce9
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/service/CustomerService.java
@@ -0,0 +1,66 @@
+package com.baeldung.boot.composite.key.service;
+
+import java.util.Optional;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+import com.baeldung.boot.composite.key.dao.CustomerRepository;
+import com.baeldung.boot.composite.key.dao.SaleRepository;
+import com.baeldung.boot.composite.key.dao.TicketRepository;
+import com.baeldung.boot.composite.key.data.Customer;
+import com.baeldung.boot.composite.key.data.Sale;
+import com.baeldung.boot.composite.key.data.Ticket;
+import com.baeldung.boot.composite.key.data.TicketId;
+
+@Service
+public class CustomerService {
+    @Autowired
+    private CustomerRepository customerRepository;
+
+    @Autowired
+    private TicketRepository ticketRepository;
+
+    @Autowired
+    private SaleRepository saleRepository;
+
+    public Optional<Ticket> find(TicketId id) {
+        return ticketRepository.findById(id);
+    }
+
+    public Ticket insert(Ticket ticket) {
+        return ticketRepository.insert(ticket);
+    }
+
+    public Ticket save(Ticket ticket) {
+        return ticketRepository.save(ticket);
+    }
+
+    public Optional<Customer> findCustomerById(String id) {
+        return customerRepository.findById(id);
+    }
+
+    public Optional<Customer> findCustomerByIndex(Long storeId, Long number) {
+        return customerRepository.findByStoreIdAndNumber(storeId, number);
+    }
+
+    public Customer insert(Customer customer) {
+        return customerRepository.insert(customer);
+    }
+
+    public Customer save(Customer customer) {
+        return customerRepository.save(customer);
+    }
+
+    public Sale insert(Sale sale) {
+        return saleRepository.insert(sale);
+    }
+
+    public Optional<Sale> findSaleByTicketId(TicketId ticketId) {
+        return saleRepository.findByTicketId(ticketId);
+    }
+
+    public Optional<Sale> findSaleById(String id) {
+        return saleRepository.findById(id);
+    }
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/web/CustomerController.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/web/CustomerController.java
new file mode 100644
index 0000000000..83afe0ae42
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/composite/key/web/CustomerController.java
@@ -0,0 +1,88 @@
+package com.baeldung.boot.composite.key.web;
+
+import java.util.Optional;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.PutMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import com.baeldung.boot.composite.key.data.Customer;
+import com.baeldung.boot.composite.key.data.Sale;
+import com.baeldung.boot.composite.key.data.Ticket;
+import com.baeldung.boot.composite.key.data.TicketId;
+import com.baeldung.boot.composite.key.service.CustomerService;
+
+@RestController
+@RequestMapping("/customer")
+public class CustomerController {
+    @Autowired
+    private CustomerService customerService;
+
+    // @Autowired
+    // private TicketRepository ticketRepository;
+    //
+    // @GetMapping("/ticket")
+    // public Optional<Ticket> getTicket(TicketId id) {
+    // return ticketRepository.findById(id);
+    // }
+    //
+    // @PostMapping("/ticket")
+    // public Ticket postTicket(@RequestBody Ticket ticket) {
+    // return ticketRepository.insert(ticket);
+    // }
+
+    @GetMapping("/ticket")
+    public Optional<Ticket> getTicket(TicketId id) {
+        return customerService.find(id);
+    }
+
+    @PostMapping("/ticket")
+    public Ticket postTicket(@RequestBody Ticket ticket) {
+        return customerService.insert(ticket);
+    }
+
+    @PutMapping("/ticket")
+    public Ticket putTicket(@RequestBody Ticket ticket) {
+        return customerService.save(ticket);
+    }
+
+    @GetMapping("/{id}")
+    public Optional<Customer> getCustomer(@PathVariable String id) {
+        return customerService.findCustomerById(id);
+    }
+
+    @GetMapping("/{storeId}/{number}")
+    public Optional<Customer> getCustomerByIndex(@PathVariable Long storeId, @PathVariable Long number) {
+        return customerService.findCustomerByIndex(storeId, number);
+    }
+
+    @PostMapping
+    public Customer postCustomer(@RequestBody Customer customer) {
+        return customerService.insert(customer);
+    }
+
+    @PutMapping
+    public Customer putCustomer(@RequestBody Customer customer) {
+        return customerService.save(customer);
+    }
+
+    @PostMapping("/sale")
+    public Sale postSale(@RequestBody Sale sale) {
+        return customerService.insert(sale);
+    }
+
+    @GetMapping("/sale/{id}")
+    public Optional<Sale> getSale(@PathVariable String id) {
+        return customerService.findSaleById(id);
+    }
+
+    @GetMapping("/sale")
+    public Optional<Sale> getSale(TicketId ticketId) {
+        return customerService.findSaleByTicketId(ticketId);
+    }
+}
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/main/resources/boot.composite.key/app.properties b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/resources/boot.composite.key/app.properties
new file mode 100644
index 0000000000..a73a94d850
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/main/resources/boot.composite.key/app.properties
@@ -0,0 +1 @@
+spring.data.mongodb.auto-index-creation=true
diff --git a/persistence-modules/spring-boot-persistence-mongodb-2/src/test/java/com/baeldung/boot/composite/key/CustomerServiceIntegrationTest.java b/persistence-modules/spring-boot-persistence-mongodb-2/src/test/java/com/baeldung/boot/composite/key/CustomerServiceIntegrationTest.java
new file mode 100644
index 0000000000..4f779ebf02
--- /dev/null
+++ b/persistence-modules/spring-boot-persistence-mongodb-2/src/test/java/com/baeldung/boot/composite/key/CustomerServiceIntegrationTest.java
@@ -0,0 +1,140 @@
+package com.baeldung.boot.composite.key;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import java.util.Optional;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.dao.DuplicateKeyException;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import com.baeldung.boot.composite.key.data.Customer;
+import com.baeldung.boot.composite.key.data.Ticket;
+import com.baeldung.boot.composite.key.data.TicketId;
+import com.baeldung.boot.composite.key.service.CustomerService;
+
+@SpringBootTest
+@DirtiesContext
+@RunWith(SpringRunner.class)
+public class CustomerServiceIntegrationTest {
+    @Autowired
+    private CustomerService service;
+
+    private static Ticket ticket;
+    private static TicketId ticketId;
+
+    @BeforeClass
+    public static void setup() {
+        ticket = new Ticket();
+        ticket.setEvent("Event A");
+
+        ticketId = new TicketId();
+        ticketId.setDate("2020-01-01");
+        ticketId.setVenue("Venue A");
+        ticket.setId(ticketId);
+    }
+
+    @Test
+    public void givenCompositeId_whenObjectSaved_thenIdMatches() {
+        Ticket savedTicket = service.insert(ticket);
+        assertEquals(savedTicket.getId(), ticket.getId());
+    }
+
+    @Test
+    public void givenCompositeId_whenSearchingByIdObject_thenFound() {
+        Optional<Ticket> optionalTicket = service.find(ticketId);
+
+        assertThat(optionalTicket.isPresent());
+        Ticket savedTicket = optionalTicket.get();
+
+        assertEquals(savedTicket.getId(), ticketId);
+    }
+
+    @Test
+    public void givenCompoundUniqueIndex_whenSearchingByGeneratedId_thenFound() {
+        Customer customer = new Customer();
+        customer.setName("Name");
+        customer.setNumber(0l);
+        customer.setStoreId(0l);
+
+        Customer savedCustomer = service.insert(customer);
+
+        Optional<Customer> optional = service.findCustomerById(savedCustomer.getId());
+
+        assertThat(optional.isPresent());
+    }
+
+    @Test
+    public void givenCompositeId_whenDupeInsert_thenExceptionIsThrown() {
+        Ticket ticket = new Ticket();
+        ticket.setEvent("C");
+
+        TicketId ticketId = new TicketId();
+        ticketId.setDate("2020-01-01");
+        ticketId.setVenue("V");
+        ticket.setId(ticketId);
+
+        assertThrows(DuplicateKeyException.class, () -> {
+            service.insert(ticket);
+            service.insert(ticket);
+        });
+    }
+
+    @Test
+    public void givenCompositeId_whenDupeSave_thenObjectUpdated() {
+        TicketId ticketId = new TicketId();
+        ticketId.setDate("2020-01-01");
+        ticketId.setVenue("Venue");
+
+        Ticket ticketA = new Ticket();
+        ticketA.setEvent("A");
+        ticketA.setId(ticketId);
+
+        service.save(ticketA);
+
+        Ticket ticketB = new Ticket();
+        ticketB.setEvent("B");
+        ticketB.setId(ticketId);
+
+        Ticket savedTicket = service.save(ticketB);
+        assertEquals(savedTicket.getEvent(), ticketB.getEvent());
+    }
+
+    @Test
+    public void givenCompoundUniqueIndex_whenDupeInsert_thenExceptionIsThrown() {
+        Customer customer = new Customer();
+        customer.setName("Name");
+        customer.setNumber(1l);
+        customer.setStoreId(2l);
+
+        assertThrows(DuplicateKeyException.class, () -> {
+            service.insert(customer);
+            service.insert(customer);
+        });
+    }
+
+    @Test
+    public void givenCompoundUniqueIndex_whenDupeSave_thenExceptionIsThrown() {
+        Customer customerA = new Customer();
+        customerA.setName("Name A");
+        customerA.setNumber(1l);
+        customerA.setStoreId(2l);
+
+        Customer customerB = new Customer();
+        customerB.setName("Name B");
+        customerB.setNumber(1l);
+        customerB.setStoreId(2l);
+
+        assertThrows(DuplicateKeyException.class, () -> {
+            service.save(customerA);
+            service.save(customerB);
+        });
+    }
+}