diff --git a/src/main/java/de/mlessmann/certassist/models/Certificate.java b/src/main/java/de/mlessmann/certassist/models/Certificate.java
index 1cf9644..f7a5997 100644
--- a/src/main/java/de/mlessmann/certassist/models/Certificate.java
+++ b/src/main/java/de/mlessmann/certassist/models/Certificate.java
@@ -19,9 +19,7 @@ public class Certificate {
     private String id;
 
     @NotNull
-    private String oid;
-
-    @NotNull
+    @Enumerated(EnumType.STRING)
     private CertificateType type;
 
     @NotNull
diff --git a/src/main/java/de/mlessmann/certassist/models/User.java b/src/main/java/de/mlessmann/certassist/models/User.java
index 78f77a4..42a221e 100644
--- a/src/main/java/de/mlessmann/certassist/models/User.java
+++ b/src/main/java/de/mlessmann/certassist/models/User.java
@@ -4,6 +4,7 @@ import jakarta.persistence.Entity;
 import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.GenerationType;
 import jakarta.persistence.Id;
+import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.Setter;
 
@@ -12,8 +13,9 @@ import lombok.Setter;
 public class User {
 
     @Id
-    @GeneratedValue(strategy = GenerationType.SEQUENCE)
-    private Long id;
+    @GeneratedValue(strategy = GenerationType.UUID)
+    @Setter(AccessLevel.NONE)
+    private String id;
 
     @Setter
     private String username;
diff --git a/src/main/java/de/mlessmann/certassist/openssl/CertificateRequest.java b/src/main/java/de/mlessmann/certassist/openssl/CertificateRequest.java
index 4d6ab9d..54befcd 100644
--- a/src/main/java/de/mlessmann/certassist/openssl/CertificateRequest.java
+++ b/src/main/java/de/mlessmann/certassist/openssl/CertificateRequest.java
@@ -9,6 +9,7 @@ import lombok.Data;
 public class CertificateRequest {
 
     @Builder.Default
+    @Deprecated
     private String oid = UUID.randomUUID().toString();
 
     private RequestType type;
diff --git a/src/main/java/de/mlessmann/certassist/repositories/CertificateRepository.java b/src/main/java/de/mlessmann/certassist/repositories/CertificateRepository.java
index ba15b30..fed956f 100644
--- a/src/main/java/de/mlessmann/certassist/repositories/CertificateRepository.java
+++ b/src/main/java/de/mlessmann/certassist/repositories/CertificateRepository.java
@@ -5,6 +5,4 @@ import org.springframework.data.repository.CrudRepository;
 import org.springframework.stereotype.Repository;
 
 @Repository
-public interface CertificateRepository extends CrudRepository<Certificate, String> {
-    Certificate findByOid(String oid);
-}
+public interface CertificateRepository extends CrudRepository<Certificate, String> {}
diff --git a/src/main/java/de/mlessmann/certassist/repositories/UserRepository.java b/src/main/java/de/mlessmann/certassist/repositories/UserRepository.java
index 6459e0a..6839491 100644
--- a/src/main/java/de/mlessmann/certassist/repositories/UserRepository.java
+++ b/src/main/java/de/mlessmann/certassist/repositories/UserRepository.java
@@ -5,4 +5,4 @@ import org.springframework.data.repository.CrudRepository;
 import org.springframework.stereotype.Repository;
 
 @Repository
-public interface UserRepository extends CrudRepository<User, Long> {}
+public interface UserRepository extends CrudRepository<User, String> {}
diff --git a/src/test/java/de/mlessmann/certassist/repositories/CertificateExtensionRepositoryTest.java b/src/test/java/de/mlessmann/certassist/repositories/CertificateExtensionRepositoryTest.java
index c5431db..8f40ca4 100644
--- a/src/test/java/de/mlessmann/certassist/repositories/CertificateExtensionRepositoryTest.java
+++ b/src/test/java/de/mlessmann/certassist/repositories/CertificateExtensionRepositoryTest.java
@@ -1,7 +1,6 @@
 package de.mlessmann.certassist.repositories;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.junit.jupiter.api.Assertions.*;
 
 import de.mlessmann.certassist.models.CertificateExtension;
 import jakarta.transaction.Transactional;
diff --git a/src/test/java/de/mlessmann/certassist/repositories/CertificateRepositoryTest.java b/src/test/java/de/mlessmann/certassist/repositories/CertificateRepositoryTest.java
index 2db68dc..e7008fc 100644
--- a/src/test/java/de/mlessmann/certassist/repositories/CertificateRepositoryTest.java
+++ b/src/test/java/de/mlessmann/certassist/repositories/CertificateRepositoryTest.java
@@ -22,7 +22,6 @@ class CertificateRepositoryTest {
 
     private Certificate getCertificate() {
         final Certificate certificate = new Certificate();
-        certificate.setOid("test");
         certificate.setCommonName("test-cn");
         certificate.setType(CertificateType.NORMAL_CERTIFICATE);
         certificate.setRequestedKeyLength(1);
@@ -37,16 +36,9 @@ class CertificateRepositoryTest {
         final Certificate certificate = getCertificate();
         repository.save(certificate);
 
-        assertThat(repository.findById(certificate.getId()).orElseThrow().getOid()).isEqualTo("test");
-    }
-
-    @Test
-    @Transactional
-    void findCertificateByOid() {
-        final Certificate certificate = getCertificate();
-        repository.save(certificate);
-
-        assertThat(repository.findByOid("test").getCommonName()).isEqualTo("test-cn");
+        Certificate foundCertificate = repository.findById(certificate.getId()).orElseThrow();
+        assertThat(foundCertificate.getCommonName()).isEqualTo("test-cn");
+        assertThat(foundCertificate.getType()).isEqualTo(CertificateType.NORMAL_CERTIFICATE);
     }
 
     @Test