diff --git a/Cargo.toml b/Cargo.toml
index 6d5f3240..f8bab903 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,8 +18,9 @@ keywords = ["interpreter", "opa", "policy-as-code", "rego"]
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [features]
-default = ["full-opa"]
+default = ["full-opa", "arc"]
 
+arc = ["scientific/arc"]
 base64 = ["dep:data-encoding"]
 base64url = ["dep:data-encoding"]
 crypto = ["dep:constant_time_eq", "dep:hmac", "dep:hex", "dep:md-5", "dep:sha1", "dep:sha2"]
diff --git a/src/ast.rs b/src/ast.rs
index 40cb219b..4b425ba8 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 use crate::lexer::*;
+use crate::Rc;
 
 use std::ops::Deref;
 
@@ -37,7 +38,7 @@ pub enum AssignOp {
 }
 
 pub struct NodeRef<T> {
-    r: std::rc::Rc<T>,
+    r: Rc<T>,
 }
 
 impl<T> Clone for NodeRef<T> {
@@ -54,7 +55,7 @@ impl<T: std::fmt::Debug> std::fmt::Debug for NodeRef<T> {
 
 impl<T> std::cmp::PartialEq for NodeRef<T> {
     fn eq(&self, other: &Self) -> bool {
-        std::rc::Rc::as_ptr(&self.r).eq(&std::rc::Rc::as_ptr(&other.r))
+        Rc::as_ptr(&self.r).eq(&Rc::as_ptr(&other.r))
     }
 }
 
@@ -62,7 +63,7 @@ impl<T> std::cmp::Eq for NodeRef<T> {}
 
 impl<T> std::cmp::Ord for NodeRef<T> {
     fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-        std::rc::Rc::as_ptr(&self.r).cmp(&std::rc::Rc::as_ptr(&other.r))
+        Rc::as_ptr(&self.r).cmp(&Rc::as_ptr(&other.r))
     }
 }
 
@@ -88,9 +89,7 @@ impl<T> AsRef<T> for NodeRef<T> {
 
 impl<T> NodeRef<T> {
     pub fn new(t: T) -> Self {
-        Self {
-            r: std::rc::Rc::new(t),
-        }
+        Self { r: Rc::new(t) }
     }
 }
 
diff --git a/src/builtins/arrays.rs b/src/builtins/arrays.rs
index e1dea3ca..bd80d7b2 100644
--- a/src/builtins/arrays.rs
+++ b/src/builtins/arrays.rs
@@ -5,7 +5,8 @@ use crate::ast::{Expr, Ref};
 use crate::builtins;
 use crate::builtins::utils::{ensure_args_count, ensure_array, ensure_numeric};
 use crate::lexer::Span;
-use crate::value::{Rc, Value};
+use crate::Rc;
+use crate::Value;
 
 use std::collections::HashMap;
 
diff --git a/src/builtins/objects.rs b/src/builtins/objects.rs
index 3e942862..995a4ae6 100644
--- a/src/builtins/objects.rs
+++ b/src/builtins/objects.rs
@@ -5,7 +5,8 @@ use crate::ast::{Expr, Ref};
 use crate::builtins;
 use crate::builtins::utils::{ensure_args_count, ensure_array, ensure_object};
 use crate::lexer::Span;
-use crate::value::{Rc, Value};
+use crate::Rc;
+use crate::Value;
 
 use std::collections::{BTreeMap, BTreeSet, HashMap};
 use std::iter::Iterator;
diff --git a/src/builtins/utils.rs b/src/builtins/utils.rs
index a1200a52..4996e410 100644
--- a/src/builtins/utils.rs
+++ b/src/builtins/utils.rs
@@ -4,7 +4,8 @@
 use crate::ast::{Expr, Ref};
 use crate::lexer::Span;
 use crate::number::Number;
-use crate::value::{Rc, Value};
+use crate::Rc;
+use crate::Value;
 
 use std::collections::{BTreeMap, BTreeSet};
 
diff --git a/src/engine.rs b/src/engine.rs
index f1d64c6e..2de5af94 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -17,7 +17,7 @@ use anyhow::{bail, Result};
 
 /// The Rego evaluation engine.
 ///
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct Engine {
     modules: Vec<Ref<Module>>,
     interpreter: Interpreter,
@@ -120,6 +120,11 @@ impl Engine {
         self.interpreter.set_input(input);
     }
 
+    pub fn set_input_json(&mut self, input_json: &str) -> Result<()> {
+        self.set_input(Value::from_json_str(input_json)?);
+        Ok(())
+    }
+
     /// Clear the data document.
     ///
     /// The data document will be reset to an empty object.
@@ -182,6 +187,10 @@ impl Engine {
         self.interpreter.get_data_mut().merge(data)
     }
 
+    pub fn add_data_json(&mut self, data_json: &str) -> Result<()> {
+        self.add_data(Value::from_json_str(data_json)?)
+    }
+
     /// Set whether builtins should raise errors strictly or not.
     ///
     /// Regorus differs from OPA in that by default builtins will
@@ -256,6 +265,14 @@ impl Engine {
         )
     }
 
+    pub fn eval_bool_query(&mut self, query: String, enable_tracing: bool) -> Result<bool> {
+        let results = self.eval_query(query, enable_tracing)?;
+        if results.result.len() != 1 || results.result[0].expressions.len() != 1 {
+            bail!("query did not produce exactly one value");
+        }
+        results.result[0].expressions[0].value.as_bool().copied()
+    }
+
     #[doc(hidden)]
     fn prepare_for_eval(&mut self, enable_tracing: bool) -> Result<()> {
         self.interpreter.set_traces(enable_tracing);
diff --git a/src/interpreter.rs b/src/interpreter.rs
index 9646c231..8bf7cb2d 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -9,6 +9,7 @@ use crate::parser::Parser;
 use crate::scheduler::*;
 use crate::utils::*;
 use crate::value::*;
+use crate::Rc;
 use crate::{Expression, Extension, Location, QueryResult, QueryResults};
 
 use anyhow::{anyhow, bail, Result};
@@ -37,7 +38,7 @@ enum FunctionModifier {
     Value(Value),
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct Interpreter {
     modules: Vec<Ref<Module>>,
     module: Option<Ref<Module>>,
@@ -64,7 +65,7 @@ pub struct Interpreter {
     allow_deprecated: bool,
     strict_builtin_errors: bool,
     imports: BTreeMap<String, Ref<Expr>>,
-    extensions: HashMap<String, (u8, Box<dyn Extension>)>,
+    extensions: HashMap<String, (u8, Rc<Box<dyn Extension>>)>,
 }
 
 impl Default for Interpreter {
@@ -2165,7 +2166,7 @@ impl Interpreter {
             if param_values.len() != *nargs as usize {
                 bail!(span.error("incorrect number of parameters supplied to extension"));
             }
-            let r = ext(param_values);
+            let r = Rc::make_mut(ext)(param_values);
             // Restore with_functions.
             if let Some(with_functions) = with_functions_saved {
                 self.with_functions = with_functions;
@@ -3458,7 +3459,7 @@ impl Interpreter {
         extension: Box<dyn Extension>,
     ) -> Result<()> {
         if let std::collections::hash_map::Entry::Vacant(v) = self.extensions.entry(path) {
-            v.insert((nargs, extension));
+            v.insert((nargs, Rc::new(extension)));
             Ok(())
         } else {
             bail!("extension already added");
diff --git a/src/lexer.rs b/src/lexer.rs
index 8d8dc6f4..67aec674 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -8,7 +8,9 @@ use core::str::CharIndices;
 use std::convert::AsRef;
 use std::path::Path;
 
-use crate::value::Value;
+use crate::Rc;
+use crate::Value;
+
 use anyhow::{anyhow, bail, Result};
 
 #[derive(Clone)]
@@ -20,7 +22,7 @@ struct SourceInternal {
 
 #[derive(Clone)]
 pub struct Source {
-    src: std::rc::Rc<SourceInternal>,
+    src: Rc<SourceInternal>,
 }
 
 #[derive(Clone)]
@@ -108,7 +110,7 @@ impl Source {
             lines.push((s, s));
         }
         Self {
-            src: std::rc::Rc::new(SourceInternal {
+            src: Rc::new(SourceInternal {
                 file,
                 contents,
                 lines,
diff --git a/src/lib.rs b/src/lib.rs
index 28082199..3d91ff89 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -20,6 +20,12 @@ mod value;
 pub use engine::Engine;
 pub use value::Value;
 
+#[cfg(feature = "arc")]
+use std::sync::Arc as Rc;
+
+#[cfg(not(feature = "arc"))]
+use std::rc::Rc;
+
 /// Location of an [`Expression`] in a Rego query.
 ///
 /// ```
@@ -68,7 +74,7 @@ pub struct Expression {
     pub value: Value,
 
     /// The Rego expression.
-    pub text: std::rc::Rc<str>,
+    pub text: Rc<str>,
 
     /// Location of the expression in the query string.
     pub location: Location,
@@ -263,7 +269,7 @@ pub struct QueryResults {
 /// A user defined builtin function implementation.
 ///
 /// It is not necessary to implement this trait directly.
-pub trait Extension: FnMut(Vec<Value>) -> anyhow::Result<Value> {
+pub trait Extension: FnMut(Vec<Value>) -> anyhow::Result<Value> + Send + Sync {
     /// Fn, FnMut etc are not sized and cannot be cloned in their boxed form.
     /// clone_box exists to overcome that.
     fn clone_box<'a>(&self) -> Box<dyn 'a + Extension>
@@ -274,7 +280,7 @@ pub trait Extension: FnMut(Vec<Value>) -> anyhow::Result<Value> {
 /// Automatically make matching closures a valid [`Extension`].
 impl<F> Extension for F
 where
-    F: FnMut(Vec<Value>) -> anyhow::Result<Value> + Clone,
+    F: FnMut(Vec<Value>) -> anyhow::Result<Value> + Clone + Send + Sync,
 {
     fn clone_box<'a>(&self) -> Box<dyn 'a + Extension>
     where
@@ -291,6 +297,12 @@ impl<'a> Clone for Box<dyn 'a + Extension> {
     }
 }
 
+impl std::fmt::Debug for dyn Extension {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
+        f.write_fmt(format_args!("<extension>"))
+    }
+}
+
 /// Items in `unstable` are likely to change.
 #[doc(hidden)]
 pub mod unstable {
diff --git a/src/number.rs b/src/number.rs
index 8b7eac4f..735695dd 100644
--- a/src/number.rs
+++ b/src/number.rs
@@ -3,7 +3,6 @@
 
 use core::fmt::{Debug, Formatter};
 use std::cmp::{Ord, Ordering};
-use std::rc::Rc;
 use std::str::FromStr;
 
 use anyhow::{anyhow, bail, Result};
@@ -11,6 +10,8 @@ use anyhow::{anyhow, bail, Result};
 use serde::ser::Serializer;
 use serde::Serialize;
 
+use crate::Rc;
+
 pub type BigInt = i128;
 
 type BigFloat = scientific::Scientific;
diff --git a/src/scheduler.rs b/src/scheduler.rs
index 77c7be3e..0eb79693 100644
--- a/src/scheduler.rs
+++ b/src/scheduler.rs
@@ -380,7 +380,7 @@ pub struct Analyzer {
     current_module_path: String,
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct Schedule {
     pub scopes: BTreeMap<Ref<Query>, Scope>,
     pub order: BTreeMap<Ref<Query>, Vec<u16>>,
diff --git a/src/value.rs b/src/value.rs
index f6ccb7e8..5283feeb 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -15,7 +15,7 @@ use serde::de::{self, Deserializer, MapAccess, SeqAccess, Visitor};
 use serde::ser::{SerializeMap, Serializer};
 use serde::{Deserialize, Serialize};
 
-pub type Rc<T> = compact_rc::Rc16<T>;
+use crate::Rc;
 
 /// A value in a Rego document.
 ///
diff --git a/tests/arc.rs b/tests/arc.rs
new file mode 100644
index 00000000..528671b7
--- /dev/null
+++ b/tests/arc.rs
@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+use lazy_static::lazy_static;
+use std::sync::Mutex;
+
+use regorus::*;
+
+// Ensure that types can be s
+lazy_static! {
+    static ref VALUE: Value = Value::Null;
+    static ref ENGINE: Mutex<Engine> = Mutex::new(Engine::new());
+//    static ref ENGINE: Engine = Engine::new();
+}
+
+#[test]
+fn shared_engine() -> anyhow::Result<()> {
+    let e_guard = ENGINE.lock();
+    let mut engine = e_guard.expect("failed to lock engine");
+
+    engine.add_policy(
+        "hello.rego".to_string(),
+        r#"
+package test
+allow = true
+"#
+        .to_string(),
+    )?;
+
+    let results = engine.eval_query("data.test.allow".to_string(), false)?;
+    assert_eq!(results.result[0].expressions[0].value, Value::from(true));
+    Ok(())
+}
diff --git a/tests/mod.rs b/tests/mod.rs
index 4782498e..7e739bf3 100644
--- a/tests/mod.rs
+++ b/tests/mod.rs
@@ -5,3 +5,6 @@ mod engine;
 mod lexer;
 mod parser;
 mod value;
+
+#[cfg(feature = "arc")]
+mod arc;