diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxDocumentServiceResponse.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxDocumentServiceResponse.java
index 9b2c3fec392fb..69169607371ae 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxDocumentServiceResponse.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxDocumentServiceResponse.java
@@ -33,19 +33,10 @@ public class RxDocumentServiceResponse {
     private final StoreResponse storeResponse;
 
     public RxDocumentServiceResponse(StoreResponse response) {
-        String[] headerNames = response.getResponseHeaderNames();
-        String[] headerValues = response.getResponseHeaderValues();
-
-        this.headersMap = new HashMap<>(headerNames.length);
+        this.headersMap = response.getResponseHeaders();
 
         // Gets status code.
         this.statusCode = response.getStatus();
-
-        // Extracts headers.
-        for (int i = 0; i < headerNames.length; i++) {
-            this.headersMap.put(headerNames[i], headerValues[i]);
-        }
-
         this.storeResponse = response;
     }
 
diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxGatewayStoreModel.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxGatewayStoreModel.java
index ce161cf4ffad3..03534fffa6948 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxGatewayStoreModel.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/RxGatewayStoreModel.java
@@ -276,7 +276,7 @@ private Mono<RxDocumentServiceResponse> toDocumentServiceResponse(Mono<HttpRespo
 
                                // transforms to Observable<StoreResponse>
                                StoreResponse rsp = new StoreResponse(httpResponseStatus,
-                                   HttpUtils.unescape(httpResponseHeaders.toMap().entrySet()),
+                                   HttpUtils.unescape(httpResponseHeaders.toMap()),
                                    content);
                                DirectBridgeInternal.setRequestTimeline(rsp, reactorNettyRequestRecord.takeTimelineSnapshot());
                                if (request.requestContext.cosmosResponseDiagnostics != null) {
diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/HttpUtils.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/HttpUtils.java
index 27c4a22bc1c3a..a9db5368e0434 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/HttpUtils.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/HttpUtils.java
@@ -74,14 +74,15 @@ public static String getDateHeader(Map<String, String> headerValues) {
         return date != null ? date : StringUtils.EMPTY;
     }
 
-    public static List<Entry<String, String>> unescape(Set<Entry<String, String>> headers) {
-        List<Entry<String, String>> result = new ArrayList<>(headers.size());
-        for (Entry<String, String> entry : headers) {
-            if (entry.getKey().equals(HttpConstants.HttpHeaders.OWNER_FULL_NAME)) {
-                String unescapedUrl = HttpUtils.urlDecode(entry.getValue());
-                entry = new AbstractMap.SimpleEntry<>(entry.getKey(), unescapedUrl);
+    public static Map<String, String> unescape(Map<String, String> headers) {
+        Map<String, String> result = new HashMap<>(headers.size());
+        for (Entry<String, String> entry : headers.entrySet()) {
+            String key = entry.getKey();
+            String value = entry.getValue();
+            if (key.equals(HttpConstants.HttpHeaders.OWNER_FULL_NAME)) {
+                value = HttpUtils.urlDecode(value);
             }
-            result.add(entry);
+            result.put(key, value);
         }
         return result;
     }
diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/ResponseUtils.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/ResponseUtils.java
index 91b98158838fd..67376664abade 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/ResponseUtils.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/ResponseUtils.java
@@ -27,7 +27,7 @@ static Mono<StoreResponse> toStoreResponse(HttpResponse httpClientResponse, Http
 
         return contentObservable.map(byteArrayContent -> {
             // transforms to Mono<StoreResponse>
-            return new StoreResponse(httpClientResponse.statusCode(), HttpUtils.unescape(httpResponseHeaders.toMap().entrySet()), byteArrayContent);
+            return new StoreResponse(httpClientResponse.statusCode(), HttpUtils.unescape(httpResponseHeaders.toMap()), byteArrayContent);
         });
     }
 }
diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreClient.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreClient.java
index f2cced7ad666c..ca1ad974c8f68 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreClient.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreClient.java
@@ -128,17 +128,8 @@ private void handleUnsuccessfulStoreResponse(RxDocumentServiceRequest request, C
     private RxDocumentServiceResponse completeResponse(
         StoreResponse storeResponse,
         RxDocumentServiceRequest request) throws InternalServerErrorException {
-        if (storeResponse.getResponseHeaderNames().length != storeResponse.getResponseHeaderValues().length) {
-            throw new InternalServerErrorException(RMResources.InvalidBackendResponse);
-        }
-
-        Map<String, String> headers = new HashMap<>(storeResponse.getResponseHeaderNames().length);
-        for (int idx = 0; idx < storeResponse.getResponseHeaderNames().length; idx++) {
-            String name = storeResponse.getResponseHeaderNames()[idx];
-            String value = storeResponse.getResponseHeaderValues()[idx];
 
-            headers.put(name, value);
-        }
+        Map<String, String> headers = new HashMap<>(storeResponse.getResponseHeaders());
 
         this.updateResponseHeader(request, headers);
         this.captureSessionToken(request, headers);
diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreResponse.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreResponse.java
index a4448c21ca690..dd23139aac4d9 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreResponse.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreResponse.java
@@ -10,10 +10,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.io.InputStream;
-import java.io.UnsupportedEncodingException;
-import java.util.List;
-import java.util.Map.Entry;
+import java.util.Map;
 
 /**
  * Used internally to represents a response from the store.
@@ -21,8 +18,7 @@
 public class StoreResponse {
     final static Logger LOGGER = LoggerFactory.getLogger(StoreResponse.class);
     final private int status;
-    final private String[] responseHeaderNames;
-    final private String[] responseHeaderValues;
+    final private Map<String, String> responseHeaders;
     final private byte[] content;
 
     private CosmosResponseDiagnostics cosmosResponseDiagnostics;
@@ -30,20 +26,11 @@ public class StoreResponse {
 
     public StoreResponse(
             int status,
-            List<Entry<String, String>> headerEntries,
+            Map<String, String> headerEntries,
             byte[] content) {
 
         requestTimeline = RequestTimeline.empty();
-        responseHeaderNames = new String[headerEntries.size()];
-        responseHeaderValues = new String[headerEntries.size()];
-
-        int i = 0;
-
-        for(Entry<String, String> headerEntry: headerEntries) {
-            responseHeaderNames[i] = headerEntry.getKey();
-            responseHeaderValues[i] = headerEntry.getValue();
-            i++;
-        }
+        responseHeaders = headerEntries;
 
         this.status = status;
         this.content = content;
@@ -53,12 +40,8 @@ public int getStatus() {
         return status;
     }
 
-    public String[] getResponseHeaderNames() {
-        return responseHeaderNames;
-    }
-
-    public String[] getResponseHeaderValues() {
-        return responseHeaderValues;
+    public Map<String, String> getResponseHeaders() {
+        return this.responseHeaders;
     }
 
     public byte[] getResponseBody() {
@@ -82,18 +65,16 @@ public String getContinuation() {
         return this.getHeaderValue(HttpConstants.HttpHeaders.CONTINUATION);
     }
 
-    public String getHeaderValue(String attribute) {
-        if (this.responseHeaderValues == null || this.responseHeaderNames.length != this.responseHeaderValues.length) {
-            return null;
-        }
+    public boolean containsHeader(String key) {
+        return this.responseHeaders != null && this.responseHeaders.containsKey(key);
+    }
 
-        for (int i = 0; i < responseHeaderNames.length; i++) {
-            if (responseHeaderNames[i].equalsIgnoreCase(attribute)) {
-                return responseHeaderValues[i];
-            }
-        }
+    public String setHeaderValue(String key, String value) {
+        return this.responseHeaders.put(key, value);
+    }
 
-        return null;
+    public String getHeaderValue(String attribute) {
+        return this.responseHeaders.get(attribute);
     }
 
     public CosmosResponseDiagnostics getCosmosResponseDiagnostics() {
diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreResult.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreResult.java
index 0499e4bb843a9..7ecce38339473 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreResult.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/StoreResult.java
@@ -120,14 +120,9 @@ private static void setRequestCharge(StoreResponse response, CosmosClientExcepti
                     Double.toString(totalRequestCharge));
         }
         // Set total charge as final charge for the response.
-        else if (response.getResponseHeaderNames() != null) {
-            for (int i = 0; i < response.getResponseHeaderNames().length; ++i) {
-                if (Strings.areEqualIgnoreCase(
-                        response.getResponseHeaderNames()[i],
-                        HttpConstants.HttpHeaders.REQUEST_CHARGE)) {
-                    response.getResponseHeaderValues()[i] = Double.toString(totalRequestCharge);
-                    break;
-                }
+        else {
+            if (response.containsHeader(HttpConstants.HttpHeaders.REQUEST_CHARGE)) {
+                response.setHeaderValue(HttpConstants.HttpHeaders.REQUEST_CHARGE, Double.toString(totalRequestCharge));
             }
         }
     }
diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/rntbd/RntbdResponse.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/rntbd/RntbdResponse.java
index fc517e7b73fcb..14422b20873ba 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/rntbd/RntbdResponse.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/rntbd/RntbdResponse.java
@@ -291,14 +291,11 @@ static RntbdResponse decode(final ByteBuf in) {
     }
 
     StoreResponse toStoreResponse(final RntbdContext context) {
-
-
-
         checkNotNull(context, "context");
 
         return new StoreResponse(
             this.getStatus().code(),
-            this.headers.asList(context, this.getActivityId()),
+            this.headers.asMap(context, this.getActivityId()),
             toByteArray(this.content)
         );
     }
diff --git a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/rntbd/RntbdResponseHeaders.java b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/rntbd/RntbdResponseHeaders.java
index 70dc762ca7c04..7ef5037d674d0 100644
--- a/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/rntbd/RntbdResponseHeaders.java
+++ b/sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/directconnectivity/rntbd/RntbdResponseHeaders.java
@@ -8,13 +8,13 @@
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectWriter;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableMap;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.handler.codec.CorruptedFrameException;
 
 import java.math.BigDecimal;
 import java.util.AbstractMap;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
@@ -209,17 +209,18 @@ List<Map.Entry<String, String>> asList(final RntbdContext context, final UUID ac
 
     public Map<String, String> asMap(final RntbdContext context, final UUID activityId) {
 
-        final ImmutableMap.Builder<String, String> builder = ImmutableMap.builderWithExpectedSize(this.computeCount() + 2);
-        builder.put(new Entry(HttpHeaders.SERVER_VERSION, context.serverVersion()));
-        builder.put(new Entry(HttpHeaders.ACTIVITY_ID, activityId.toString()));
+        final HashMap<String, String> headersMap = new HashMap<>(this.computeCount() + 2);
+        headersMap.put(HttpHeaders.SERVER_VERSION, context.serverVersion());
+        headersMap.put(HttpHeaders.ACTIVITY_ID, activityId.toString());
 
         this.collectEntries((token, toEntry) -> {
             if (token.isPresent()) {
-                builder.put(toEntry.apply(token));
+                Map.Entry<String, String> entry = toEntry.apply(token);
+                headersMap.put(entry.getKey(), entry.getValue());
             }
         });
 
-        return builder.build();
+        return headersMap;
     }
 
     static RntbdResponseHeaders decode(final ByteBuf in) {
diff --git a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/RetryContextOnDiagnosticTest.java b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/RetryContextOnDiagnosticTest.java
index e24aa50423f87..08fe0e6207a31 100644
--- a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/RetryContextOnDiagnosticTest.java
+++ b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/RetryContextOnDiagnosticTest.java
@@ -29,6 +29,7 @@
 import java.lang.reflect.Field;
 import java.time.Duration;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.concurrent.Callable;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
@@ -52,7 +53,7 @@ public void backoffRetryUtilityExecuteRetry() throws Exception {
         retryPolicy = new TestRetryPolicy();
         CosmosClientException exception = new CosmosClientException(410, exceptionText);
         Mockito.when(callbackMethod.call()).thenThrow(exception, exception, exception, exception, exception)
-            .thenReturn(Mono.just(new StoreResponse(200, new ArrayList<>(), getUTF8BytesOrNull(responseText))));
+            .thenReturn(Mono.just(new StoreResponse(200, new HashMap<>(), getUTF8BytesOrNull(responseText))));
         Mono<StoreResponse> monoResponse = BackoffRetryUtility.executeRetry(callbackMethod, retryPolicy);
         StoreResponse response = validateSuccess(monoResponse);
 
@@ -88,7 +89,7 @@ public void backoffRetryUtilityExecuteAsync() {
         CosmosClientException exception = new CosmosClientException(410, exceptionText);
         Mono<CosmosClientException> exceptionMono = Mono.error(exception);
         Mockito.when(parameterizedCallbackMethod.apply(Matchers.any(Quadruple.class))).thenReturn(exceptionMono, exceptionMono, exceptionMono, exceptionMono, exceptionMono)
-            .thenReturn(Mono.just(new StoreResponse(200, new ArrayList<>(), getUTF8BytesOrNull(responseText))));
+            .thenReturn(Mono.just(new StoreResponse(200, new HashMap<>(), getUTF8BytesOrNull(responseText))));
         Mono<StoreResponse> monoResponse = BackoffRetryUtility.executeAsync(parameterizedCallbackMethod, retryPolicy, inBackoffAlternateCallbackMethod, Duration.ofSeconds(5), serviceRequest);
         StoreResponse response = validateSuccess(monoResponse);
 
diff --git a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/StoreResponseBuilder.java b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/StoreResponseBuilder.java
index 1c1442cf7c2b4..152ee9b5352bf 100644
--- a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/StoreResponseBuilder.java
+++ b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/StoreResponseBuilder.java
@@ -9,6 +9,7 @@
 import java.math.BigDecimal;
 import java.util.AbstractMap;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -16,7 +17,7 @@
 
 public class StoreResponseBuilder {
     private int status;
-    private List<Map.Entry<String, String>> headerEntries;
+    private Map<String, String> headerEntries;
     private String content;
 
     public static StoreResponseBuilder create() {
@@ -24,16 +25,16 @@ public static StoreResponseBuilder create() {
     }
 
     public StoreResponseBuilder() {
-        headerEntries = new ArrayList<>();
+        headerEntries = new HashMap<>();
     }
 
     public StoreResponseBuilder withHeader(String key, String value) {
-        headerEntries.add(new AbstractMap.SimpleEntry(key, value));
+        headerEntries.put(key, value);
         return this;
     }
 
     public StoreResponseBuilder withLSN(long lsn) {
-        headerEntries.add(new AbstractMap.SimpleEntry(WFConstants.BackendHeaders.LSN, Long.toString(lsn)));
+        headerEntries.put(WFConstants.BackendHeaders.LSN, Long.toString(lsn));
         return this;
     }
 
@@ -43,42 +44,42 @@ public StoreResponseBuilder withRequestCharge(BigDecimal requestCharge) {
     }
 
     public StoreResponseBuilder withRequestCharge(double requestCharge) {
-        headerEntries.add(new AbstractMap.SimpleEntry(HttpConstants.HttpHeaders.REQUEST_CHARGE, Double.toString(requestCharge)));
+        headerEntries.put(HttpConstants.HttpHeaders.REQUEST_CHARGE, Double.toString(requestCharge));
         return this;
     }
 
     public StoreResponseBuilder withLocalLSN(long localLsn) {
-        headerEntries.add(new AbstractMap.SimpleEntry(WFConstants.BackendHeaders.LOCAL_LSN, Long.toString(localLsn)));
+        headerEntries.put(WFConstants.BackendHeaders.LOCAL_LSN, Long.toString(localLsn));
         return this;
     }
 
     public StoreResponseBuilder withPartitionKeyRangeId(String partitionKeyRangeId) {
-        headerEntries.add(new AbstractMap.SimpleEntry(WFConstants.BackendHeaders.PARTITION_KEY_RANGE_ID, partitionKeyRangeId));
+        headerEntries.put(WFConstants.BackendHeaders.PARTITION_KEY_RANGE_ID, partitionKeyRangeId);
         return this;
     }
 
     public StoreResponseBuilder withItemLocalLSN(long itemLocalLsn) {
-        headerEntries.add(new AbstractMap.SimpleEntry(WFConstants.BackendHeaders.ITEM_LOCAL_LSN, Long.toString(itemLocalLsn)));
+        headerEntries.put(WFConstants.BackendHeaders.ITEM_LOCAL_LSN, Long.toString(itemLocalLsn));
         return this;
     }
 
     public StoreResponseBuilder withQuorumAckecdLsn(long quorumAckecdLsn) {
-        headerEntries.add(new AbstractMap.SimpleEntry(WFConstants.BackendHeaders.QUORUM_ACKED_LSN, Long.toString(quorumAckecdLsn)));
+        headerEntries.put(WFConstants.BackendHeaders.QUORUM_ACKED_LSN, Long.toString(quorumAckecdLsn));
         return this;
     }
 
     public StoreResponseBuilder withQuorumAckecdLocalLsn(long quorumAckecdLocalLsn) {
-        headerEntries.add(new AbstractMap.SimpleEntry(WFConstants.BackendHeaders.QUORUM_ACKED_LOCAL_LSN, Long.toString(quorumAckecdLocalLsn)));
+        headerEntries.put(WFConstants.BackendHeaders.QUORUM_ACKED_LOCAL_LSN, Long.toString(quorumAckecdLocalLsn));
         return this;
     }
 
     public StoreResponseBuilder withGlobalCommittedLsn(long globalCommittedLsn) {
-        headerEntries.add(new AbstractMap.SimpleEntry(WFConstants.BackendHeaders.GLOBAL_COMMITTED_LSN, Long.toString(globalCommittedLsn)));
+        headerEntries.put(WFConstants.BackendHeaders.GLOBAL_COMMITTED_LSN, Long.toString(globalCommittedLsn));
         return this;
     }
 
     public StoreResponseBuilder withSessionToken(String sessionToken) {
-        headerEntries.add(new AbstractMap.SimpleEntry(HttpConstants.HttpHeaders.SESSION_TOKEN, sessionToken));
+        headerEntries.put(HttpConstants.HttpHeaders.SESSION_TOKEN, sessionToken);
         return this;
     }
 
diff --git a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/ConsistencyWriterTest.java b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/ConsistencyWriterTest.java
index 8d363c4f1947b..1b84edd1dcbd3 100644
--- a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/ConsistencyWriterTest.java
+++ b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/ConsistencyWriterTest.java
@@ -16,6 +16,7 @@
 import com.azure.cosmos.implementation.StoreResponseBuilder;
 import com.azure.cosmos.implementation.Utils;
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
 import io.reactivex.subscribers.TestSubscriber;
 import org.mockito.Mockito;
 import org.mockito.invocation.InvocationOnMock;
@@ -145,10 +146,12 @@ public void run() {
 
     @Test(groups = "unit")
     public void getLsnAndGlobalCommittedLsn() {
-        ImmutableList.Builder<Map.Entry<String, String>> builder = new ImmutableList.Builder<>();
-        builder.add(new AbstractMap.SimpleEntry<>(WFConstants.BackendHeaders.LSN, "3"));
-        builder.add(new AbstractMap.SimpleEntry<>(WFConstants.BackendHeaders.GLOBAL_COMMITTED_LSN, "2"));
-        ImmutableList<Map.Entry<String, String>> headers = builder.build();
+
+        ImmutableMap.Builder<String, String> builder = new ImmutableMap.Builder<>();
+
+        builder.put(WFConstants.BackendHeaders.LSN, "3");
+        builder.put(WFConstants.BackendHeaders.GLOBAL_COMMITTED_LSN, "2");
+        ImmutableMap<String, String> headers = builder.build();
 
         StoreResponse sr = new StoreResponse(0, headers, null);
         Utils.ValueHolder<Long> lsn = Utils.ValueHolder.initialize(-2l);
diff --git a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/HttpUtilsTest.java b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/HttpUtilsTest.java
index d79a2bff8f784..66c18d678c369 100644
--- a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/HttpUtilsTest.java
+++ b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/HttpUtilsTest.java
@@ -9,6 +9,7 @@
 import org.testng.annotations.Test;
 
 import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
 
@@ -17,7 +18,7 @@
 public class HttpUtilsTest {
 
     private static final String OWNER_FULL_NAME_VALUE = "dbs/RxJava.SDKTest.SharedDatabase_20190304T121302_iZc/colls/+%20-_,:.%7C~b2d67001-9000-454e-a140-abceb1756c48%20+-_,:.%7C~";
-    
+
     @Test(groups = { "unit" })
     public void verifyConversionOfHttpResponseHeadersToMap() {
         HttpHeaders headersMap = new HttpHeaders(1);
@@ -27,13 +28,13 @@ public void verifyConversionOfHttpResponseHeadersToMap() {
         Mockito.when(httpResponse.headers()).thenReturn(headersMap);
         HttpHeaders httpResponseHeaders = httpResponse.headers();
         Set<Entry<String, String>> resultHeadersSet = HttpUtils.asMap(httpResponseHeaders).entrySet();
-        
+
         assertThat(resultHeadersSet.size()).isEqualTo(1);
         Entry<String, String> entry = resultHeadersSet.iterator().next();
         assertThat(entry.getKey()).isEqualTo(HttpConstants.HttpHeaders.OWNER_FULL_NAME);
         assertThat(entry.getValue()).isEqualTo(HttpUtils.urlDecode(OWNER_FULL_NAME_VALUE));
-        
-        List<Entry<String, String>> resultHeadersList = HttpUtils.unescape(httpResponseHeaders.toMap().entrySet());
+
+        Map<String, String> resultHeadersList = HttpUtils.unescape(httpResponseHeaders.toMap());
         assertThat(resultHeadersList.size()).isEqualTo(1);
         entry = resultHeadersSet.iterator().next();
         assertThat(entry.getKey()).isEqualTo(HttpConstants.HttpHeaders.OWNER_FULL_NAME);
diff --git a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/StoreResponseTest.java b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/StoreResponseTest.java
index 569abe5d51fc7..219b673dfbc85 100644
--- a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/StoreResponseTest.java
+++ b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/StoreResponseTest.java
@@ -19,7 +19,7 @@ public void stringContent() {
         headerMap.put("key1", "value1");
         headerMap.put("key2", "value2");
 
-        StoreResponse sp = new StoreResponse(200, new ArrayList<>(headerMap.entrySet()), getUTF8BytesOrNull(content));
+        StoreResponse sp = new StoreResponse(200, headerMap, getUTF8BytesOrNull(content));
 
         assertThat(sp.getStatus()).isEqualTo(200);
         assertThat(sp.getResponseBody()).isEqualTo(getUTF8BytesOrNull(content));
diff --git a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/StoreResponseValidator.java b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/StoreResponseValidator.java
index 6b1fc7ceaf206..024159116ad46 100644
--- a/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/StoreResponseValidator.java
+++ b/sdk/cosmos/azure-cosmos/src/test/java/com/azure/cosmos/implementation/directconnectivity/StoreResponseValidator.java
@@ -40,7 +40,7 @@ public Builder hasHeader(String headerKey) {
             validators.add(new StoreResponseValidator() {
                 @Override
                 public void validate(StoreResponse resp) {
-                    assertThat(Arrays.asList(resp.getResponseHeaderNames())).asList().contains(headerKey);
+                    assertThat(resp.getResponseHeaders().keySet()).contains(headerKey);
                 }
             });
             return this;
@@ -50,9 +50,8 @@ public Builder withHeader(String headerKey, String headerValue) {
             validators.add(new StoreResponseValidator() {
                 @Override
                 public void validate(StoreResponse resp) {
-                    assertThat(Arrays.asList(resp.getResponseHeaderNames())).asList().contains(headerKey);
-                    int index = Arrays.asList(resp.getResponseHeaderNames()).indexOf(headerKey);
-                    assertThat(resp.getResponseHeaderValues()[index]).isEqualTo(headerValue);
+                    assertThat(resp.getResponseHeaders().keySet()).contains(headerKey);
+                    assertThat(resp.getResponseHeaders().get(headerKey)).isEqualTo(headerValue);
                 }
             });
             return this;
@@ -63,10 +62,9 @@ public Builder withHeaderValueCondition(String headerKey, Condition<String> cond
             validators.add(new StoreResponseValidator() {
                 @Override
                 public void validate(StoreResponse resp) {
-                    assertThat(Arrays.asList(resp.getResponseHeaderNames())).asList().contains(headerKey);
-                    int index = Arrays.asList(resp.getResponseHeaderNames()).indexOf(headerKey);
-                    String value = resp.getResponseHeaderValues()[index];
-                    condition.matches(value);
+                    assertThat(resp.getResponseHeaders().keySet()).contains(headerKey);
+                    String headerValue = resp.getResponseHeaders().get(headerKey);
+                    condition.matches(headerValue);
                 }
             });
             return this;