diff --git a/src/core/tests.rs b/src/core/tests.rs
index aaa8628bd0..be3d4369b0 100644
--- a/src/core/tests.rs
+++ b/src/core/tests.rs
@@ -1,12 +1,16 @@
+use std::path::PathBuf;
+
+use tempfile::TempDir;
+
 use crate::collector::Count;
-use crate::directory::{RamDirectory, WatchCallback};
-use crate::indexer::NoMergePolicy;
+use crate::directory::{RamDirectory, RoRamDirectory, WatchCallback};
+use crate::indexer::{LogMergePolicy, NoMergePolicy};
+use crate::postings::Postings;
 use crate::query::TermQuery;
 use crate::schema::{Field, IndexRecordOption, Schema, INDEXED, STRING, TEXT};
 use crate::tokenizer::TokenizerManager;
 use crate::{
-    Directory, Document, Index, IndexBuilder, IndexReader, IndexSettings, ReloadPolicy, SegmentId,
-    Term,
+    Directory, Document, Index, IndexBuilder, IndexReader, IndexSettings, IndexWriter, ReloadPolicy, SegmentId, Term
 };
 
 #[test]
@@ -344,3 +348,35 @@ fn test_merging_segment_update_docfreq() {
     let term_info = inv_index.get_term_info(&term).unwrap().unwrap();
     assert_eq!(term_info.doc_freq, 12);
 }
+
+#[test]
+fn test_read_only_dir() -> crate::Result<()> {
+    let schema = throw_away_schema();
+    let field = schema.get_field("num_likes").unwrap();
+    let tempdir = TempDir::new().unwrap();
+    let tempdir_path = PathBuf::from(tempdir.path());
+
+    let mut write_index = Index::create_in_dir(&tempdir_path, schema.clone())?;
+
+    // let mut index = Index::create_from_tempdir(schema)?;
+    let mut writer: IndexWriter = write_index.writer_for_tests()?;
+    writer.commit()?;
+    let dir = RoRamDirectory::new(&tempdir_path).unwrap();
+    let mut index = Index::open_or_create(dir, schema.clone())?;
+    let reader = index
+        .reader_builder()
+        .reload_policy(ReloadPolicy::Manual)
+        .try_into()?;
+    assert_eq!(reader.searcher().num_docs(), 0);
+    writer.add_document(doc!(field=>1u64))?;
+    let (sender, receiver) = crossbeam_channel::unbounded();
+    let _handle = index.directory_mut().watch(WatchCallback::new(move || {
+        let _ = sender.send(());
+    }));
+    writer.commit()?;
+    assert!(receiver.recv().is_ok());
+    assert_eq!(reader.searcher().num_docs(), 0);
+    reader.reload()?;
+    assert_eq!(reader.searcher().num_docs(), 1);
+    Ok(())
+}
diff --git a/src/directory/mmap_directory.rs b/src/directory/mmap_directory.rs
index 7419cbe49b..9588132a13 100644
--- a/src/directory/mmap_directory.rs
+++ b/src/directory/mmap_directory.rs
@@ -297,9 +297,9 @@ impl MmapDirectory {
 /// uses BSD locks (`flock`). The lock is actually released when
 /// the `File` object is dropped and its associated file descriptor
 /// is closed.
-struct ReleaseLockFile {
-    _file: File,
-    path: PathBuf,
+pub(crate) struct ReleaseLockFile {
+    pub(crate) _file: File,
+    pub(crate) path: PathBuf,
 }
 
 impl Drop for ReleaseLockFile {
diff --git a/src/directory/mod.rs b/src/directory/mod.rs
index 1dda8579e9..6c7e57c6d5 100644
--- a/src/directory/mod.rs
+++ b/src/directory/mod.rs
@@ -10,6 +10,7 @@ mod footer;
 mod managed_directory;
 mod ram_directory;
 mod watch_event_router;
+mod roram_directory;
 
 /// Errors specific to the directory module.
 pub mod error;
@@ -27,6 +28,7 @@ pub use self::directory::{Directory, DirectoryClone, DirectoryLock};
 pub use self::directory_lock::{Lock, INDEX_WRITER_LOCK, META_LOCK};
 pub use self::ram_directory::RamDirectory;
 pub use self::watch_event_router::{WatchCallback, WatchCallbackList, WatchHandle};
+pub use self::roram_directory::RoRamDirectory;
 
 /// Outcome of the Garbage collection
 pub struct GarbageCollectionResult {
diff --git a/src/directory/roram_directory.rs b/src/directory/roram_directory.rs
new file mode 100644
index 0000000000..2355575465
--- /dev/null
+++ b/src/directory/roram_directory.rs
@@ -0,0 +1,212 @@
+use std::{
+    collections::HashMap,
+    fs::{File, OpenOptions},
+    io::{self, Read, Write},
+    path::{Path, PathBuf},
+    sync::{Arc, RwLock},
+};
+
+use common::file_slice::FileSlice;
+use fs4::FileExt;
+
+use crate::core::META_FILEPATH;
+
+use super::{
+    error::{LockError, OpenReadError, OpenWriteError},
+    file_watcher::FileWatcher,
+    mmap_directory::ReleaseLockFile,
+    Directory, DirectoryLock, META_LOCK,
+};
+
+/// RoRamDirectory is a read only directory that stores data in RAM.
+/// Note: please make sure the index files exist before creating a RoRamDirectory.
+#[derive(Clone)]
+pub struct RoRamDirectory {
+    inner: Arc<RwLock<RoRamDirectoryInner>>,
+}
+
+impl RoRamDirectory {
+    pub fn new(dir: &Path) -> Result<RoRamDirectory, std::io::Error> {
+        Ok(RoRamDirectory {
+            inner: Arc::new(RwLock::new(RoRamDirectoryInner::new(dir)?)),
+        })
+    }
+}
+
+impl std::fmt::Debug for RoRamDirectory {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("RoRamDirectory").finish()
+    }
+}
+
+impl Directory for RoRamDirectory {
+    fn get_file_handle(
+        &self,
+        path: &std::path::Path,
+    ) -> Result<std::sync::Arc<dyn common::file_slice::FileHandle>, super::error::OpenReadError>
+    {
+        let file_slice = self.open_read(path)?;
+        Ok(Arc::new(file_slice))
+    }
+
+    fn open_read(&self, path: &Path) -> Result<FileSlice, super::error::OpenReadError> {
+        self.inner.write().unwrap().open_read(path)
+    }
+
+    fn delete(&self, path: &std::path::Path) -> Result<(), super::error::DeleteError> {
+        self.inner.write().unwrap().delete(path);
+        Ok(())
+    }
+
+    fn exists(&self, path: &std::path::Path) -> Result<bool, super::error::OpenReadError> {
+        Ok(self.inner.read().unwrap().exists(path))
+    }
+
+    fn open_write(
+        &self,
+        path: &std::path::Path,
+    ) -> Result<super::WritePtr, super::error::OpenWriteError> {
+        unimplemented!()
+    }
+
+    fn acquire_lock(
+        &self,
+        lock: &super::Lock,
+    ) -> Result<super::DirectoryLock, super::error::LockError> {
+        let full_path = self.inner.read().unwrap().root_path.join(&lock.filepath);
+        // We make sure that the file exists.
+        let file: File = OpenOptions::new()
+            .write(true)
+            .create(true) //< if the file does not exist yet, create it.
+            .truncate(false)
+            .open(full_path)
+            .map_err(LockError::wrap_io_error)?;
+        if lock.is_blocking {
+            file.lock_exclusive().map_err(LockError::wrap_io_error)?;
+        } else {
+            file.try_lock_exclusive().map_err(|_| LockError::LockBusy)?
+        }
+        // dropping the file handle will release the lock.
+        Ok(DirectoryLock::from(Box::new(ReleaseLockFile {
+            path: lock.filepath.clone(),
+            _file: file,
+        })))
+    }
+
+    fn atomic_read(&self, path: &std::path::Path) -> Result<Vec<u8>, super::error::OpenReadError> {
+        let full_path = self.inner.read().unwrap().root_path.join(path);
+        let mut buffer = Vec::new();
+        match File::open(full_path) {
+            Ok(mut file) => {
+                file.read_to_end(&mut buffer).map_err(|io_error| {
+                    OpenReadError::wrap_io_error(io_error, path.to_path_buf())
+                })?;
+                Ok(buffer)
+            }
+            Err(io_error) => {
+                if io_error.kind() == io::ErrorKind::NotFound {
+                    Err(OpenReadError::FileDoesNotExist(path.to_owned()))
+                } else {
+                    Err(OpenReadError::wrap_io_error(io_error, path.to_path_buf()))
+                }
+            }
+        }
+    }
+
+    fn atomic_write(&self, _path: &std::path::Path, _data: &[u8]) -> std::io::Result<()> {
+        unimplemented!("RoRamDirectory is read-only")
+    }
+
+    fn sync_directory(&self) -> std::io::Result<()> {
+        Ok(())
+    }
+
+    fn watch(&self, watch_callback: super::WatchCallback) -> crate::Result<super::WatchHandle> {
+        self.inner.read().unwrap().watch(watch_callback)
+    }
+}
+
+struct RoRamDirectoryInner {
+    root_path: PathBuf,
+    files: HashMap<PathBuf, FileSlice>,
+    watcher: FileWatcher,
+}
+
+fn open_file(path: &Path) -> Result<FileSlice, std::io::Error> {
+    let mut file = File::open(path)?;
+    let mut data = Vec::new();
+    file.read_to_end(&mut data)?;
+    let file_slice = FileSlice::from(data);
+    Ok(file_slice)
+}
+
+impl RoRamDirectoryInner {
+    fn new(dir: &Path) -> Result<RoRamDirectoryInner, std::io::Error> {
+        // read all files in the directory
+        let mut files: HashMap<PathBuf, FileSlice> = HashMap::new();
+        for entry in std::fs::read_dir(dir)? {
+            let entry = entry?;
+            let path = entry.path();
+            if !entry.file_type()?.is_file() {
+                warn!("Skipping non-file {:?}", path);
+                continue;
+            }
+            let file_slice = open_file(&path)?;
+            files.insert(entry.file_name().into(), file_slice);
+        }
+        Ok(RoRamDirectoryInner {
+            root_path: dir.to_path_buf(),
+            files,
+            watcher: FileWatcher::new(&dir.join(*META_FILEPATH)),
+        })
+    }
+
+    fn open_read(&mut self, path: &Path) -> Result<FileSlice, super::error::OpenReadError> {
+        let slice = self.files.get(path).cloned();
+        match slice {
+            Some(slice) => Ok(slice),
+            None => {
+                let full_path = self.root_path.join(path);
+                let file_slice = open_file(&full_path)
+                    .map_err(|io_error| OpenReadError::wrap_io_error(io_error, full_path))?;
+                self.files.insert(path.to_path_buf(), file_slice.clone());
+                Ok(file_slice)
+            }
+        }
+    }
+
+    fn exists(&self, path: &Path) -> bool {
+        self.files.contains_key(path)
+    }
+
+    fn watch(&self, watch_callback: super::WatchCallback) -> crate::Result<super::WatchHandle> {
+        Ok(self.watcher.watch(watch_callback))
+    }
+
+    fn delete(&mut self, path: &Path) {
+        self.files.remove(path);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Write;
+
+    #[test]
+    fn test_ro_ram_directory() {
+        let dir = tempfile::tempdir().unwrap();
+        let dir_path = dir.path();
+        let file_name = Path::new("test.txt");
+        let file_path = dir_path.join(file_name);
+        let mut file = File::create(&file_path).unwrap();
+        file.write_all(b"hello world").unwrap();
+
+        let ram_dir = RoRamDirectory::new(dir_path).unwrap();
+
+        let file_slice = ram_dir.open_read(&file_name).unwrap();
+        assert_eq!(file_slice.read_bytes().unwrap().as_slice(), b"hello world");
+
+        assert!(ram_dir.exists(&file_name).unwrap());
+    }
+}