diff --git a/pom.xml b/pom.xml
index c40c88c..aaa405f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -21,7 +21,7 @@
         <jgit.version>4.11.0.201803080745-r</jgit.version>
         <junit.version>5.2.0</junit.version>
         <assertj.version>3.10.0</assertj.version>
-        <mon.version>0.7.0</mon.version>
+        <mon.version>0.8.0</mon.version>
         <mockito.version>2.18.3</mockito.version>
         <java-semver.version>0.9.0</java-semver.version>
     </properties>
diff --git a/src/main/java/net/kemitix/gitdb/impl/GitDBBranchImpl.java b/src/main/java/net/kemitix/gitdb/impl/GitDBBranchImpl.java
index 9b90a36..92b495b 100644
--- a/src/main/java/net/kemitix/gitdb/impl/GitDBBranchImpl.java
+++ b/src/main/java/net/kemitix/gitdb/impl/GitDBBranchImpl.java
@@ -31,7 +31,6 @@ import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 
-import java.io.IOException;
 import java.util.function.Function;
 
 /**
@@ -81,14 +80,10 @@ class GitDBBranchImpl implements GitDBBranch {
 
     @Override
     public Result<GitDBBranch> put(final String key, final String value) {
-        try {
-            final ObjectId newTree = gitDBRepo.writeValue(branchRef, KEY_PREFIX + key, value);
-            final String message = String.format("Add key [%s] = [%s]", key, value);
-            final Result<Ref> newBranch = gitDBRepo.writeCommit(branchRef, newTree, message, userName, userEmailAddress);
-            return newBranch.flatMap(b -> select(b, gitDBRepo, userName, userEmailAddress));
-        } catch (IOException e) {
-            return Result.error(e);
-        }
+        final String message = String.format("Add key [%s] = [%s]", key, value);
+        return gitDBRepo.writeValue(branchRef, KEY_PREFIX + key, value)
+                .flatMap(nt -> gitDBRepo.writeCommit(branchRef, nt, message, userName, userEmailAddress))
+                .flatMap(nb -> select(nb, gitDBRepo, userName, userEmailAddress));
     }
 
     @Override
diff --git a/src/main/java/net/kemitix/gitdb/impl/GitDBRepo.java b/src/main/java/net/kemitix/gitdb/impl/GitDBRepo.java
index ffc12c3..3a9e1ab 100644
--- a/src/main/java/net/kemitix/gitdb/impl/GitDBRepo.java
+++ b/src/main/java/net/kemitix/gitdb/impl/GitDBRepo.java
@@ -65,12 +65,11 @@ class GitDBRepo {
      * @param key     the key to insert
      * @param valueId id of the value
      * @return the id of the inserted tree
-     * @throws IOException the tree could not be stored
      */
-    ObjectId insertNewTree(
+    Result<ObjectId> insertNewTree(
             final String key,
             final ObjectId valueId
-    ) throws IOException {
+    ) {
         return keyWriter.writeFirst(key, valueId);
     }
 
@@ -94,11 +93,7 @@ class GitDBRepo {
     }
 
     private Result<Stream<NamedRevBlob>> streamTree(final Ref branchRef, final GitTreeReader treeFilter) {
-        try {
-            return Result.ok(treeFilter.stream(branchRef));
-        } catch (IOException e) {
-            return Result.error(e);
-        }
+        return treeFilter.stream(branchRef);
     }
 
     /**
@@ -110,11 +105,10 @@ class GitDBRepo {
      * @param key       the key to place the value under
      * @param value     the value
      * @return the id of the updated tree containing the update
-     * @throws IOException if there was an error writing the value
      */
-    ObjectId writeValue(final Ref branchRef, final String key, final String value) throws IOException {
-        final ObjectId blob = valueWriter.write(value.getBytes(StandardCharsets.UTF_8));
-        return keyWriter.write(key, blob, branchRef);
+    Result<ObjectId> writeValue(final Ref branchRef, final String key, final String value) {
+        return valueWriter.write(value.getBytes(StandardCharsets.UTF_8))
+                .flatMap(b -> keyWriter.write(key, b, branchRef));
     }
 
     /**
diff --git a/src/main/java/net/kemitix/gitdb/impl/GitTreeReader.java b/src/main/java/net/kemitix/gitdb/impl/GitTreeReader.java
index 5abd235..76c82f7 100644
--- a/src/main/java/net/kemitix/gitdb/impl/GitTreeReader.java
+++ b/src/main/java/net/kemitix/gitdb/impl/GitTreeReader.java
@@ -23,15 +23,20 @@ package net.kemitix.gitdb.impl;
 
 import lombok.AccessLevel;
 import lombok.RequiredArgsConstructor;
+import net.kemitix.mon.result.Result;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevTree;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.treewalk.filter.PathFilter;
 import org.eclipse.jgit.treewalk.filter.TreeFilter;
 
-import java.io.IOException;
 import java.util.Optional;
+import java.util.concurrent.Callable;
+import java.util.function.Consumer;
+import java.util.function.Function;
 import java.util.stream.Stream;
 
 /**
@@ -51,23 +56,55 @@ class GitTreeReader {
      *
      * @param branchRef the branch to read
      * @return a stream of key/value pairs as NamedRevBlobs
-     * @throws IOException if there is an error reading the commit or walking the tree
      */
-    Stream<NamedRevBlob> stream(final Ref branchRef) throws IOException {
+    Result<Stream<NamedRevBlob>> stream(final Ref branchRef) {
         final TreeWalk treeWalk = new TreeWalk(repository);
         final RevWalk revWalk = new RevWalk(repository);
-        treeWalk.addTree(revWalk.parseCommit(branchRef.getObjectId()).getTree());
-        treeWalk.setRecursive(false);
-        Optional.ofNullable(treeFilter)
-                .ifPresent(treeWalk::setFilter);
-        final Stream.Builder<NamedRevBlob> builder = Stream.builder();
-        while (treeWalk.next()) {
-            builder.add(new NamedRevBlob(
-                    treeWalk.getNameString(),
-                    revWalk.lookupBlob(treeWalk.getObjectId(0)),
-                    repository));
-        }
-        return builder.build();
+        return Result.of(parseBranchCommit(branchRef, revWalk))
+                .map(RevCommit::getTree)
+                .flatMap(addTreeTo(treeWalk))
+                .peek(disableRecursion(treeWalk))
+                .peek(setTreeFilter(treeWalk))
+                .flatMap(streamMatching(treeWalk, revWalk));
+    }
+
+    private Function<Void, Result<Stream<NamedRevBlob>>> streamMatching(
+            final TreeWalk treeWalk,
+            final RevWalk revWalk
+    ) {
+        return x -> Result.of(() -> {
+            final Stream.Builder<NamedRevBlob> builder = Stream.builder();
+            while (treeWalk.next()) {
+                builder.add(namedRevBlob(treeWalk, revWalk));
+            }
+            return builder.build();
+        });
+    }
+
+    private NamedRevBlob namedRevBlob(TreeWalk treeWalk, RevWalk revWalk) {
+        return new NamedRevBlob(
+                treeWalk.getNameString(),
+                revWalk.lookupBlob(treeWalk.getObjectId(0)),
+                repository);
+    }
+
+    private Consumer<Void> setTreeFilter(TreeWalk treeWalk) {
+        return x -> Optional.ofNullable(treeFilter).ifPresent(treeWalk::setFilter);
+    }
+
+    private Consumer<Void> disableRecursion(TreeWalk treeWalk) {
+        return x -> treeWalk.setRecursive(false);
+    }
+
+    private Function<RevTree, Result<Void>> addTreeTo(TreeWalk treeWalk) {
+        return tree -> Result.of(() -> {
+            treeWalk.addTree(tree);
+            return null;
+        });
+    }
+
+    private Callable<RevCommit> parseBranchCommit(Ref branchRef, RevWalk revWalk) {
+        return () -> revWalk.parseCommit(branchRef.getObjectId());
     }
 
     /**
@@ -77,7 +114,7 @@ class GitTreeReader {
      * @return the GitTreeReader
      */
     GitTreeReader treeFilter(final String path) {
-        this.treeFilter = PathFilter.create(path);
+        treeFilter = PathFilter.create(path);
         return this;
     }
 
diff --git a/src/main/java/net/kemitix/gitdb/impl/InitGitDBRepo.java b/src/main/java/net/kemitix/gitdb/impl/InitGitDBRepo.java
index 25b4fb4..41004bd 100644
--- a/src/main/java/net/kemitix/gitdb/impl/InitGitDBRepo.java
+++ b/src/main/java/net/kemitix/gitdb/impl/InitGitDBRepo.java
@@ -79,13 +79,16 @@ class InitGitDBRepo {
         return dbDir;
     }
 
-    private void createInitialBranchOnMaster(final Repository repository) throws IOException {
+    private Result<Void> createInitialBranchOnMaster(final Repository repository) {
         final GitDBRepo repo = new GitDBRepo(repository);
-        final ValueWriter valueWriter = new ValueWriter(repository);
-        final ObjectId objectId = valueWriter.write(new FormatVersion().toBytes());
-        final ObjectId treeId = repo.insertNewTree(GIT_DB_VERSION, objectId);
-        final ObjectId commitId = repo.initialCommit(treeId, INIT_MESSAGE, INIT_USER, INIT_EMAIL);
-        createBranch(repository, commitId, MASTER);
+        return new ValueWriter(repository)
+                .write(new FormatVersion().toBytes())
+                .flatMap(oid -> repo.insertNewTree(GIT_DB_VERSION, oid))
+                .flatMap(tid -> Result.of(() -> repo.initialCommit(tid, INIT_MESSAGE, INIT_USER, INIT_EMAIL)))
+                .flatMap(cid -> Result.of(() -> {
+                    createBranch(repository, cid, MASTER);
+                    return null;
+                }));
     }
 
     private void verifyIsNotAFile(final File dbDir) throws NotDirectoryException {
@@ -102,14 +105,17 @@ class InitGitDBRepo {
         }
     }
 
-    private void createBranch(
+    private Result<Void> createBranch(
             final Repository repository,
             final ObjectId commitId,
             final String branchName
-    ) throws IOException {
+    ) {
         final Path branchRefPath = branchRefPath(repository, branchName);
         final byte[] commitIdBytes = commitId.name().getBytes(StandardCharsets.UTF_8);
-        Files.write(branchRefPath, commitIdBytes);
+        return Result.of(() -> {
+            Files.write(branchRefPath, commitIdBytes);
+            return null;
+        });
     }
 
     private Path branchRefPath(
diff --git a/src/main/java/net/kemitix/gitdb/impl/KeyRemover.java b/src/main/java/net/kemitix/gitdb/impl/KeyRemover.java
index 6146f0c..392e540 100644
--- a/src/main/java/net/kemitix/gitdb/impl/KeyRemover.java
+++ b/src/main/java/net/kemitix/gitdb/impl/KeyRemover.java
@@ -51,16 +51,12 @@ class KeyRemover {
     Result<Maybe<ObjectId>> remove(final Ref branchRef, final String key) {
         final TreeFormatter treeFormatter = new TreeFormatter();
         final AtomicBoolean removed = new AtomicBoolean(false);
-        try {
-            new GitTreeReader(repository)
-                    .stream(branchRef)
-                    .peek(flagIfFound(key, removed))
-                    .filter(isNotKey(key))
-                    .forEach(addToTree(treeFormatter));
-            return insertTree(treeFormatter).maybe(oi -> removed.get());
-        } catch (IOException e) {
-            return Result.error(e);
-        }
+        new GitTreeReader(repository)
+                .stream(branchRef)
+                .peek(s -> s.peek(flagIfFound(key, removed))
+                        .filter(isNotKey(key))
+                        .forEach(addToTree(treeFormatter)));
+        return insertTree(treeFormatter).maybe(oi -> removed.get());
     }
 
     /**
diff --git a/src/main/java/net/kemitix/gitdb/impl/KeyWriter.java b/src/main/java/net/kemitix/gitdb/impl/KeyWriter.java
index 1dc00c1..0c7364b 100644
--- a/src/main/java/net/kemitix/gitdb/impl/KeyWriter.java
+++ b/src/main/java/net/kemitix/gitdb/impl/KeyWriter.java
@@ -21,10 +21,9 @@
 
 package net.kemitix.gitdb.impl;
 
+import net.kemitix.mon.result.Result;
 import org.eclipse.jgit.lib.*;
 
-import java.io.IOException;
-
 /**
  * Writes Keys into the Git Repository.
  *
@@ -48,42 +47,41 @@ class KeyWriter {
     /**
      * Write the first key into a new tree.
      *
-     * @param key the key
+     * @param key     the key
      * @param valueId the id of the value
      * @return the id of the new tree
-     * @throws IOException if there is an error writing the key
      */
-    ObjectId writeFirst(final String key, final ObjectId valueId) throws IOException {
+    Result<ObjectId> writeFirst(final String key, final ObjectId valueId) {
         return writeTree(key, valueId, new TreeFormatter());
     }
 
     /**
      * Write the key into a tree.
      *
-     * @param key the key
-     * @param valueId the id of the value
+     * @param key       the key
+     * @param valueId   the id of the value
      * @param branchRef the branch whose tree should be updated
      * @return the id of the updated tree
-     * @throws IOException if there is an error writing the key
      */
-    ObjectId write(final String key, final ObjectId valueId, final Ref branchRef) throws IOException {
-        return writeTree(key, valueId, getTreeFormatter(branchRef));
+    Result<ObjectId> write(final String key, final ObjectId valueId, final Ref branchRef) {
+        return getTreeFormatter(branchRef)
+                .flatMap(f -> writeTree(key, valueId, f));
     }
 
-    private TreeFormatter getTreeFormatter(final Ref branchRef) throws IOException {
+    private Result<TreeFormatter> getTreeFormatter(final Ref branchRef) {
         final TreeFormatter treeFormatter = new TreeFormatter();
         final GitTreeReader gitTreeReader = new GitTreeReader(repository);
-        gitTreeReader.stream(branchRef)
-                .forEach(item -> treeFormatter.append(item.getName(), item.getRevBlob()));
-        return treeFormatter;
+        return gitTreeReader.stream(branchRef)
+                .peek(s -> s.forEach(item -> treeFormatter.append(item.getName(), item.getRevBlob())))
+                .map(x -> treeFormatter);
     }
 
-    private ObjectId writeTree(
+    private Result<ObjectId> writeTree(
             final String key,
             final ObjectId valueId,
             final TreeFormatter treeFormatter
-    ) throws IOException {
+    ) {
         treeFormatter.append(key, FileMode.REGULAR_FILE, valueId);
-        return objectInserter.insert(treeFormatter);
+        return Result.of(() -> objectInserter.insert(treeFormatter));
     }
 }
diff --git a/src/main/java/net/kemitix/gitdb/impl/ValueWriter.java b/src/main/java/net/kemitix/gitdb/impl/ValueWriter.java
index f066551..7fa9b37 100644
--- a/src/main/java/net/kemitix/gitdb/impl/ValueWriter.java
+++ b/src/main/java/net/kemitix/gitdb/impl/ValueWriter.java
@@ -21,13 +21,12 @@
 
 package net.kemitix.gitdb.impl;
 
+import net.kemitix.mon.result.Result;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectInserter;
 import org.eclipse.jgit.lib.Repository;
 
-import java.io.IOException;
-
 /**
  * Writes Values into the Git Repository.
  *
@@ -51,9 +50,8 @@ class ValueWriter {
      *
      * @param blob the value blob
      * @return the id of the value object
-     * @throws IOException if there is an error writing the value
      */
-    ObjectId write(final byte[] blob) throws IOException {
-        return objectInserter.insert(Constants.OBJ_BLOB, blob);
+    Result<ObjectId> write(final byte[] blob) {
+        return Result.of(() -> objectInserter.insert(Constants.OBJ_BLOB, blob));
     }
 }