diff --git a/client/src/main/java/org/asynchttpclient/Realm.java b/client/src/main/java/org/asynchttpclient/Realm.java
index cf770dafe..b41203dd1 100644
--- a/client/src/main/java/org/asynchttpclient/Realm.java
+++ b/client/src/main/java/org/asynchttpclient/Realm.java
@@ -25,6 +25,7 @@
 import java.nio.charset.Charset;
 import java.security.MessageDigest;
 import java.security.SecureRandom;
+import java.util.Base64;
 import java.util.Map;
 
 import static java.nio.charset.StandardCharsets.ISO_8859_1;
@@ -70,6 +71,7 @@ public class Realm {
     private final boolean userhash;
     private final @Nullable String sid;
     private final int maxIterationCount;
+    private @Nullable String basicAuthHeader;
 
     private Realm(@Nullable AuthScheme scheme,
                   @Nullable String principal,
@@ -245,6 +247,23 @@ public int getMaxIterationCount() {
         return maxIterationCount;
     }
 
+    /**
+     * Returns the lazily computed and cached HTTP Basic authorization header for this immutable realm.
+     * Concurrent first calls may compute the same value more than once.
+     *
+     * @return the Basic authorization header
+     * @since 3.0.12
+     */
+    public String getBasicAuthHeader() {
+        String header = basicAuthHeader;
+        if (header == null) {
+            String s = principal + ':' + password;
+            header = "Basic " + Base64.getEncoder().encodeToString(s.getBytes(charset));
+            basicAuthHeader = header;
+        }
+        return header;
+    }
+
     @Override
     public String toString() {
         return "Realm{" +
diff --git a/client/src/main/java/org/asynchttpclient/util/AuthenticatorUtils.java b/client/src/main/java/org/asynchttpclient/util/AuthenticatorUtils.java
index 66d2b73b3..c6dcd34f2 100644
--- a/client/src/main/java/org/asynchttpclient/util/AuthenticatorUtils.java
+++ b/client/src/main/java/org/asynchttpclient/util/AuthenticatorUtils.java
@@ -32,7 +32,6 @@
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.security.MessageDigest;
-import java.util.Base64;
 import java.util.List;
 import java.util.Set;
 
@@ -87,12 +86,7 @@ private AuthenticatorUtils() {
     }
 
     private static @Nullable String computeBasicAuthentication(@Nullable Realm realm) {
-        return realm != null ? computeBasicAuthentication(realm.getPrincipal(), realm.getPassword(), realm.getCharset()) : null;
-    }
-
-    private static String computeBasicAuthentication(@Nullable String principal, @Nullable String password, Charset charset) {
-        String s = principal + ':' + password;
-        return "Basic " + Base64.getEncoder().encodeToString(s.getBytes(charset));
+        return realm != null ? realm.getBasicAuthHeader() : null;
     }
 
     public static String computeRealmURI(Uri uri, boolean useAbsoluteURI, boolean omitQuery) {
diff --git a/client/src/test/java/org/asynchttpclient/util/AuthenticatorUtilsTest.java b/client/src/test/java/org/asynchttpclient/util/AuthenticatorUtilsTest.java
index c98f19483..eea6cd5bc 100644
--- a/client/src/test/java/org/asynchttpclient/util/AuthenticatorUtilsTest.java
+++ b/client/src/test/java/org/asynchttpclient/util/AuthenticatorUtilsTest.java
@@ -40,12 +40,32 @@
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
 public class AuthenticatorUtilsTest {
+    @Test
+    void preemptiveBasicAuthorizationHeaderIsMemoizedOnRealm() {
+        Request request = new RequestBuilder("GET")
+                .setUrl("http://example.com/api/users")
+                .build();
+        Realm realm = new Realm.Builder("user", "pass")
+                .setScheme(Realm.AuthScheme.BASIC)
+                .setUsePreemptiveAuth(true)
+                .build();
+
+        String first = AuthenticatorUtils.perRequestAuthorizationHeader(request, realm);
+        String second = AuthenticatorUtils.perRequestAuthorizationHeader(request, realm);
+        String proxy = AuthenticatorUtils.perRequestProxyAuthorizationHeader(request, realm);
+
+        assertEquals("Basic dXNlcjpwYXNz", first);
+        assertSame(first, second);
+        assertSame(first, proxy);
+    }
+
     @Test
     void computeBodyHashEmptyBody() throws Exception {
         Request request = new RequestBuilder("GET")