diff --git a/lib/sparesults/src/csv.rs b/lib/sparesults/src/csv.rs
index ac02c99e..985092b4 100644
--- a/lib/sparesults/src/csv.rs
+++ b/lib/sparesults/src/csv.rs
@@ -628,7 +628,6 @@ mod tests {
 
     use super::*;
     use std::error::Error;
-    use std::rc::Rc;
 
     fn build_example() -> (Vec<Variable>, Vec<Vec<Option<Term>>>) {
         (
@@ -682,7 +681,6 @@ mod tests {
         let (variables, solutions) = build_example();
         let mut buffer = String::new();
         let writer = InnerCsvSolutionsWriter::start(&mut buffer, variables.clone());
-        let variables = Rc::new(variables);
         for solution in solutions {
             writer.write(
                 &mut buffer,
@@ -702,7 +700,6 @@ mod tests {
         // Write
         let mut buffer = String::new();
         let writer = InnerTsvSolutionsWriter::start(&mut buffer, variables.clone());
-        let variables = Rc::new(variables);
         for solution in &solutions {
             writer.write(
                 &mut buffer,
diff --git a/lib/sparesults/src/parser.rs b/lib/sparesults/src/parser.rs
index 8833f9ac..b0aad24c 100644
--- a/lib/sparesults/src/parser.rs
+++ b/lib/sparesults/src/parser.rs
@@ -6,7 +6,7 @@ use crate::solution::QuerySolution;
 use crate::xml::{XmlQueryResultsReader, XmlSolutionsReader};
 use oxrdf::Variable;
 use std::io::Read;
-use std::rc::Rc;
+use std::sync::Arc;
 
 /// Parsers for [SPARQL query](https://www.w3.org/TR/sparql11-query/) results serialization formats.
 ///
@@ -81,7 +81,7 @@ impl QueryResultsParser {
                     solutions,
                     variables,
                 } => FromReadQueryResultsReader::Solutions(FromReadSolutionsReader {
-                    variables: Rc::new(variables),
+                    variables: variables.into(),
                     solutions: SolutionsReaderKind::Xml(solutions),
                 }),
             },
@@ -91,7 +91,7 @@ impl QueryResultsParser {
                     solutions,
                     variables,
                 } => FromReadQueryResultsReader::Solutions(FromReadSolutionsReader {
-                    variables: Rc::new(variables),
+                    variables: variables.into(),
                     solutions: SolutionsReaderKind::Json(solutions),
                 }),
             },
@@ -102,7 +102,7 @@ impl QueryResultsParser {
                     solutions,
                     variables,
                 } => FromReadQueryResultsReader::Solutions(FromReadSolutionsReader {
-                    variables: Rc::new(variables),
+                    variables: variables.into(),
                     solutions: SolutionsReaderKind::Tsv(solutions),
                 }),
             },
@@ -166,9 +166,8 @@ pub enum FromReadQueryResultsReader<R: Read> {
 /// }
 /// # Result::<(),sparesults::ParseError>::Ok(())
 /// ```
-#[allow(clippy::rc_buffer)]
 pub struct FromReadSolutionsReader<R: Read> {
-    variables: Rc<Vec<Variable>>,
+    variables: Arc<[Variable]>,
     solutions: SolutionsReaderKind<R>,
 }
 
@@ -209,7 +208,7 @@ impl<R: Read> Iterator for FromReadSolutionsReader<R> {
                 SolutionsReaderKind::Tsv(reader) => reader.read_next(),
             }
             .transpose()?
-            .map(|values| (Rc::clone(&self.variables), values).into()),
+            .map(|values| (Arc::clone(&self.variables), values).into()),
         )
     }
 }
diff --git a/lib/sparesults/src/solution.rs b/lib/sparesults/src/solution.rs
index 842bc7d3..3990ab79 100644
--- a/lib/sparesults/src/solution.rs
+++ b/lib/sparesults/src/solution.rs
@@ -4,7 +4,7 @@ use oxrdf::{Term, Variable, VariableRef};
 use std::fmt;
 use std::iter::Zip;
 use std::ops::Index;
-use std::rc::Rc;
+use std::sync::Arc;
 
 /// Tuple associating variables and terms that are the result of a SPARQL query.
 ///
@@ -18,9 +18,8 @@ use std::rc::Rc;
 /// assert_eq!(solution.get("foo"), Some(&Literal::from(1).into())); // Get the value of the variable ?foo if it exists (here yes).
 /// assert_eq!(solution.get(1), None); // Get the value of the second column if it exists (here no).
 /// ```
-#[allow(clippy::rc_buffer)]
 pub struct QuerySolution {
-    variables: Rc<Vec<Variable>>,
+    variables: Arc<[Variable]>,
     values: Vec<Option<Term>>,
 }
 
@@ -116,7 +115,7 @@ impl QuerySolution {
     }
 }
 
-impl<V: Into<Rc<Vec<Variable>>>, S: Into<Vec<Option<Term>>>> From<(V, S)> for QuerySolution {
+impl<V: Into<Arc<[Variable]>>, S: Into<Vec<Option<Term>>>> From<(V, S)> for QuerySolution {
     #[inline]
     fn from((v, s): (V, S)) -> Self {
         Self {
diff --git a/lib/src/sparql/eval.rs b/lib/src/sparql/eval.rs
index 413fcd20..c5b35a95 100644
--- a/lib/src/sparql/eval.rs
+++ b/lib/src/sparql/eval.rs
@@ -1,10 +1,11 @@
 use crate::model::vocab::{rdf, xsd};
-use crate::model::{BlankNode, LiteralRef, NamedNode, NamedNodeRef, Term, Triple};
+use crate::model::{BlankNode, LiteralRef, NamedNodeRef, Term, Triple};
 use crate::sparql::algebra::{Query, QueryDataset};
 use crate::sparql::dataset::DatasetView;
 use crate::sparql::error::EvaluationError;
 use crate::sparql::model::*;
 use crate::sparql::service::ServiceHandler;
+use crate::sparql::CustomFunctionRegistry;
 use crate::storage::numeric_encoder::*;
 use crate::storage::small_string::SmallString;
 use digest::Digest;
@@ -35,6 +36,7 @@ use std::hash::{Hash, Hasher};
 use std::iter::Iterator;
 use std::iter::{empty, once};
 use std::rc::Rc;
+use std::sync::Arc;
 use std::{fmt, io, str};
 
 const REGEX_SIZE_LIMIT: usize = 1_000_000;
@@ -119,15 +121,14 @@ impl IntoIterator for EncodedTuple {
 }
 
 type EncodedTuplesIterator = Box<dyn Iterator<Item = Result<EncodedTuple, EvaluationError>>>;
-type CustomFunctionRegistry = HashMap<NamedNode, Rc<dyn Fn(&[Term]) -> Option<Term>>>;
 
 #[derive(Clone)]
 pub struct SimpleEvaluator {
     dataset: Rc<DatasetView>,
     base_iri: Option<Rc<Iri<String>>>,
     now: DateTime,
-    service_handler: Rc<dyn ServiceHandler<Error = EvaluationError>>,
-    custom_functions: Rc<CustomFunctionRegistry>,
+    service_handler: Arc<dyn ServiceHandler<Error = EvaluationError>>,
+    custom_functions: Arc<CustomFunctionRegistry>,
     run_stats: bool,
 }
 
@@ -135,8 +136,8 @@ impl SimpleEvaluator {
     pub fn new(
         dataset: Rc<DatasetView>,
         base_iri: Option<Rc<Iri<String>>>,
-        service_handler: Rc<dyn ServiceHandler<Error = EvaluationError>>,
-        custom_functions: Rc<CustomFunctionRegistry>,
+        service_handler: Arc<dyn ServiceHandler<Error = EvaluationError>>,
+        custom_functions: Arc<CustomFunctionRegistry>,
         run_stats: bool,
     ) -> Self {
         Self {
@@ -149,7 +150,6 @@ impl SimpleEvaluator {
         }
     }
 
-    #[allow(clippy::rc_buffer)]
     pub fn evaluate_select(&self, pattern: &GraphPattern) -> (QueryResults, Rc<EvalNodeWithStats>) {
         let mut variables = Vec::new();
         let (eval, stats) = self.graph_pattern_evaluator(pattern, &mut variables);
@@ -158,7 +158,7 @@ impl SimpleEvaluator {
             QueryResults::Solutions(decode_bindings(
                 Rc::clone(&self.dataset),
                 eval(from),
-                Rc::from(variables),
+                Arc::from(variables),
             )),
             stats,
         )
@@ -3127,11 +3127,10 @@ pub(super) fn compile_pattern(pattern: &str, flags: Option<&str>) -> Option<Rege
     regex_builder.build().ok()
 }
 
-#[allow(clippy::rc_buffer)]
 fn decode_bindings(
     dataset: Rc<DatasetView>,
     iter: EncodedTuplesIterator,
-    variables: Rc<Vec<Variable>>,
+    variables: Arc<[Variable]>,
 ) -> QuerySolutionIter {
     let tuple_size = variables.len();
     QuerySolutionIter::new(
@@ -3223,15 +3222,15 @@ fn equals(a: &EncodedTerm, b: &EncodedTerm) -> Option<bool> {
         EncodedTerm::FloatLiteral(a) => match b {
             EncodedTerm::FloatLiteral(b) => Some(a == b),
             EncodedTerm::DoubleLiteral(b) => Some(Double::from(*a) == *b),
-            EncodedTerm::IntegerLiteral(b) => Some(*a == Float::from(*b)),
+            EncodedTerm::IntegerLiteral(b) => Some(*a == (*b).into()),
             EncodedTerm::DecimalLiteral(b) => Some(*a == (*b).into()),
             _ if b.is_unknown_typed_literal() => None,
             _ => Some(false),
         },
         EncodedTerm::DoubleLiteral(a) => match b {
-            EncodedTerm::FloatLiteral(b) => Some(*a == Double::from(*b)),
+            EncodedTerm::FloatLiteral(b) => Some(*a == (*b).into()),
             EncodedTerm::DoubleLiteral(b) => Some(a == b),
-            EncodedTerm::IntegerLiteral(b) => Some(*a == Double::from(*b)),
+            EncodedTerm::IntegerLiteral(b) => Some(*a == (*b).into()),
             EncodedTerm::DecimalLiteral(b) => Some(*a == (*b).into()),
             _ if b.is_unknown_typed_literal() => None,
             _ => Some(false),
@@ -3247,7 +3246,7 @@ fn equals(a: &EncodedTerm, b: &EncodedTerm) -> Option<bool> {
         EncodedTerm::DecimalLiteral(a) => match b {
             EncodedTerm::FloatLiteral(b) => Some(Float::from(*a) == *b),
             EncodedTerm::DoubleLiteral(b) => Some(Double::from(*a) == *b),
-            EncodedTerm::IntegerLiteral(b) => Some(*a == Decimal::from(*b)),
+            EncodedTerm::IntegerLiteral(b) => Some(*a == (*b).into()),
             EncodedTerm::DecimalLiteral(b) => Some(a == b),
             _ if b.is_unknown_typed_literal() => None,
             _ => Some(false),
diff --git a/lib/src/sparql/mod.rs b/lib/src/sparql/mod.rs
index 1972a77e..262ab868 100644
--- a/lib/src/sparql/mod.rs
+++ b/lib/src/sparql/mod.rs
@@ -30,6 +30,7 @@ use sparopt::algebra::GraphPattern;
 use sparopt::Optimizer;
 use std::collections::HashMap;
 use std::rc::Rc;
+use std::sync::Arc;
 use std::time::Duration;
 use std::{fmt, io};
 
@@ -56,7 +57,7 @@ pub(crate) fn evaluate_query(
                 Rc::new(dataset),
                 base_iri.map(Rc::new),
                 options.service_handler(),
-                Rc::new(options.custom_functions),
+                Arc::new(options.custom_functions),
                 run_stats,
             )
             .evaluate_select(&pattern);
@@ -76,7 +77,7 @@ pub(crate) fn evaluate_query(
                 Rc::new(dataset),
                 base_iri.map(Rc::new),
                 options.service_handler(),
-                Rc::new(options.custom_functions),
+                Arc::new(options.custom_functions),
                 run_stats,
             )
             .evaluate_ask(&pattern);
@@ -99,7 +100,7 @@ pub(crate) fn evaluate_query(
                 Rc::new(dataset),
                 base_iri.map(Rc::new),
                 options.service_handler(),
-                Rc::new(options.custom_functions),
+                Arc::new(options.custom_functions),
                 run_stats,
             )
             .evaluate_construct(&pattern, &template);
@@ -119,7 +120,7 @@ pub(crate) fn evaluate_query(
                 Rc::new(dataset),
                 base_iri.map(Rc::new),
                 options.service_handler(),
-                Rc::new(options.custom_functions),
+                Arc::new(options.custom_functions),
                 run_stats,
             )
             .evaluate_describe(&pattern);
@@ -155,19 +156,22 @@ pub(crate) fn evaluate_query(
 /// ```
 #[derive(Clone, Default)]
 pub struct QueryOptions {
-    service_handler: Option<Rc<dyn ServiceHandler<Error = EvaluationError>>>,
-    custom_functions: HashMap<NamedNode, Rc<dyn Fn(&[Term]) -> Option<Term>>>,
+    service_handler: Option<Arc<dyn ServiceHandler<Error = EvaluationError>>>,
+    custom_functions: CustomFunctionRegistry,
     http_timeout: Option<Duration>,
     http_redirection_limit: usize,
     without_optimizations: bool,
 }
 
+pub(crate) type CustomFunctionRegistry =
+    HashMap<NamedNode, Arc<dyn (Fn(&[Term]) -> Option<Term>) + Send + Sync>>;
+
 impl QueryOptions {
     /// Use a given [`ServiceHandler`] to execute [SPARQL 1.1 Federated Query](https://www.w3.org/TR/sparql11-federated-query/) SERVICE calls.
     #[inline]
     #[must_use]
     pub fn with_service_handler(mut self, service_handler: impl ServiceHandler + 'static) -> Self {
-        self.service_handler = Some(Rc::new(ErrorConversionServiceHandler::wrap(
+        self.service_handler = Some(Arc::new(ErrorConversionServiceHandler::wrap(
             service_handler,
         )));
         self
@@ -177,7 +181,7 @@ impl QueryOptions {
     #[inline]
     #[must_use]
     pub fn without_service_handler(mut self) -> Self {
-        self.service_handler = Some(Rc::new(EmptyServiceHandler));
+        self.service_handler = Some(Arc::new(EmptyServiceHandler));
         self
     }
 
@@ -227,21 +231,21 @@ impl QueryOptions {
     pub fn with_custom_function(
         mut self,
         name: NamedNode,
-        evaluator: impl Fn(&[Term]) -> Option<Term> + 'static,
+        evaluator: impl Fn(&[Term]) -> Option<Term> + Send + Sync + 'static,
     ) -> Self {
-        self.custom_functions.insert(name, Rc::new(evaluator));
+        self.custom_functions.insert(name, Arc::new(evaluator));
         self
     }
 
-    fn service_handler(&self) -> Rc<dyn ServiceHandler<Error = EvaluationError>> {
+    fn service_handler(&self) -> Arc<dyn ServiceHandler<Error = EvaluationError>> {
         self.service_handler.clone().unwrap_or_else(|| {
             if cfg!(feature = "http-client") {
-                Rc::new(service::SimpleServiceHandler::new(
+                Arc::new(service::SimpleServiceHandler::new(
                     self.http_timeout,
                     self.http_redirection_limit,
                 ))
             } else {
-                Rc::new(EmptyServiceHandler)
+                Arc::new(EmptyServiceHandler)
             }
         })
     }
diff --git a/lib/src/sparql/model.rs b/lib/src/sparql/model.rs
index 0c7becc6..81712877 100644
--- a/lib/src/sparql/model.rs
+++ b/lib/src/sparql/model.rs
@@ -8,7 +8,7 @@ use crate::sparql::results::{
 use oxrdf::{Variable, VariableRef};
 pub use sparesults::QuerySolution;
 use std::io::{Read, Write};
-use std::rc::Rc;
+use std::sync::Arc;
 
 /// Results of a [SPARQL query](https://www.w3.org/TR/sparql11-query/).
 pub enum QueryResults {
@@ -170,22 +170,20 @@ impl<R: Read + 'static> From<FromReadQueryResultsReader<R>> for QueryResults {
 /// }
 /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
 /// ```
-#[allow(clippy::rc_buffer)]
 pub struct QuerySolutionIter {
-    variables: Rc<Vec<Variable>>,
+    variables: Arc<[Variable]>,
     iter: Box<dyn Iterator<Item = Result<QuerySolution, EvaluationError>>>,
 }
 
 impl QuerySolutionIter {
-    #[allow(clippy::rc_buffer)]
     pub fn new(
-        variables: Rc<Vec<Variable>>,
+        variables: Arc<[Variable]>,
         iter: impl Iterator<Item = Result<Vec<Option<Term>>, EvaluationError>> + 'static,
     ) -> Self {
         Self {
-            variables: Rc::clone(&variables),
+            variables: Arc::clone(&variables),
             iter: Box::new(
-                iter.map(move |t| t.map(|values| (Rc::clone(&variables), values).into())),
+                iter.map(move |t| t.map(|values| (Arc::clone(&variables), values).into())),
             ),
         }
     }
@@ -211,7 +209,7 @@ impl QuerySolutionIter {
 impl<R: Read + 'static> From<FromReadSolutionsReader<R>> for QuerySolutionIter {
     fn from(reader: FromReadSolutionsReader<R>) -> Self {
         Self {
-            variables: Rc::new(reader.variables().to_vec()),
+            variables: reader.variables().into(),
             iter: Box::new(reader.map(|t| t.map_err(EvaluationError::from))),
         }
     }
@@ -291,10 +289,12 @@ mod tests {
                 QueryResults::Boolean(true),
                 QueryResults::Boolean(false),
                 QueryResults::Solutions(QuerySolutionIter::new(
-                    Rc::new(vec![
+                    [
                         Variable::new_unchecked("foo"),
                         Variable::new_unchecked("bar"),
-                    ]),
+                    ]
+                    .as_ref()
+                    .into(),
                     Box::new(
                         vec![
                             Ok(vec![None, None]),
diff --git a/lib/src/sparql/service.rs b/lib/src/sparql/service.rs
index dec189ae..2ec0b7a3 100644
--- a/lib/src/sparql/service.rs
+++ b/lib/src/sparql/service.rs
@@ -48,7 +48,7 @@ use std::time::Duration;
 /// }
 /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
 /// ```
-pub trait ServiceHandler {
+pub trait ServiceHandler: Send + Sync {
     type Error: Error + Send + Sync + 'static;
 
     /// Evaluates a [`Query`] against a given service identified by a [`NamedNode`].
diff --git a/lib/src/sparql/update.rs b/lib/src/sparql/update.rs
index 1744c464..2e318c71 100644
--- a/lib/src/sparql/update.rs
+++ b/lib/src/sparql/update.rs
@@ -19,6 +19,7 @@ use sparopt::Optimizer;
 use std::collections::HashMap;
 use std::io;
 use std::rc::Rc;
+use std::sync::Arc;
 
 pub fn evaluate_update<'a, 'b: 'a>(
     transaction: &'a mut StorageWriter<'b>,
@@ -131,7 +132,7 @@ impl<'a, 'b: 'a> SimpleUpdateEvaluator<'a, 'b> {
             Rc::clone(&dataset),
             self.base_iri.clone(),
             self.options.query_options.service_handler(),
-            Rc::new(self.options.query_options.custom_functions.clone()),
+            Arc::new(self.options.query_options.custom_functions.clone()),
             false,
         );
         let mut variables = Vec::new();
diff --git a/lib/src/storage/numeric_encoder.rs b/lib/src/storage/numeric_encoder.rs
index 59f7532f..fd0d7544 100644
--- a/lib/src/storage/numeric_encoder.rs
+++ b/lib/src/storage/numeric_encoder.rs
@@ -8,8 +8,8 @@ use siphasher::sip128::{Hasher128, SipHasher24};
 use std::fmt::Debug;
 use std::hash::Hash;
 use std::hash::Hasher;
-use std::rc::Rc;
 use std::str;
+use std::sync::Arc;
 
 #[derive(Eq, PartialEq, Debug, Clone, Copy, Hash)]
 #[repr(transparent)]
@@ -96,7 +96,7 @@ pub enum EncodedTerm {
     DurationLiteral(Duration),
     YearMonthDurationLiteral(YearMonthDuration),
     DayTimeDurationLiteral(DayTimeDuration),
-    Triple(Rc<EncodedTriple>),
+    Triple(Arc<EncodedTriple>),
 }
 
 impl PartialEq for EncodedTerm {
@@ -471,7 +471,7 @@ impl From<DayTimeDuration> for EncodedTerm {
 
 impl From<EncodedTriple> for EncodedTerm {
     fn from(value: EncodedTriple) -> Self {
-        Self::Triple(Rc::new(value))
+        Self::Triple(Arc::new(value))
     }
 }
 
@@ -634,7 +634,7 @@ impl From<GraphNameRef<'_>> for EncodedTerm {
 
 impl From<TripleRef<'_>> for EncodedTerm {
     fn from(triple: TripleRef<'_>) -> Self {
-        Self::Triple(Rc::new(triple.into()))
+        Self::Triple(Arc::new(triple.into()))
     }
 }