diff --git a/Cargo.toml b/Cargo.toml
index b9e0868..f168510 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2021"
 authors = ["Manuel Holtgrewe <manuel.holtgrewe@bih-charite.de>"]
 description = "Port of biocommons/hgvs to Rust"
 license = "Apache-2.0"
-homepage = "https://github.com/bihealth/seqrepo-rs"
+homepage = "https://github.com/bihealth/hgvs-rs"
 readme = "README.md"
 rust-version = "1.64.0"
 
@@ -27,7 +27,7 @@ postgres = { version = "0.19", features = ["with-chrono-0_4"] }
 quick_cache = "0.3"
 regex = "1.7"
 rustc-hash = "1.1"
-seqrepo = { version = "0.5" }
+seqrepo = { version = "0.6" }
 serde_json = "1.0"
 serde = { version = "1.0", features = ["derive"] }
 thiserror = "1.0"
diff --git a/src/data/cdot/json.rs b/src/data/cdot/json.rs
index 8264356..12ae1f8 100644
--- a/src/data/cdot/json.rs
+++ b/src/data/cdot/json.rs
@@ -2,13 +2,13 @@
 //!
 //! https://github.com/SACGF/cdot
 
-use std::{collections::HashMap, path::PathBuf, rc::Rc, time::Instant};
+use std::{collections::HashMap, path::PathBuf, sync::Arc, time::Instant};
 
 use crate::{
     data::error::Error,
     data::interface::{
-        GeneInfoRecord, Provider as ProviderInterface, TxExonsRecord, TxForRegionRecord,
-        TxIdentityInfo, TxInfoRecord, TxMappingOptionsRecord, TxSimilarityRecord,
+        self, GeneInfoRecord, TxExonsRecord, TxForRegionRecord, TxIdentityInfo, TxInfoRecord,
+        TxMappingOptionsRecord, TxSimilarityRecord,
     },
     static_data::{Assembly, ASSEMBLY_INFOS},
 };
@@ -16,7 +16,7 @@ use crate::{
 use bio::data_structures::interval_tree::ArrayBackedIntervalTree;
 use chrono::NaiveDateTime;
 use indexmap::IndexMap;
-use seqrepo::{Interface as SeqRepoInterface, SeqRepo};
+use seqrepo::{self, SeqRepo};
 
 /// Configurationf or the `data::cdot::Provider`.
 #[derive(Debug, PartialEq, Clone)]
@@ -42,7 +42,7 @@ pub struct Config {
 /// `exon_aln_id`.
 pub struct Provider {
     inner: TxProvider,
-    seqrepo: Rc<dyn SeqRepoInterface>,
+    seqrepo: Arc<dyn seqrepo::Interface + Sync + Send>,
 }
 
 impl Provider {
@@ -70,14 +70,14 @@ impl Provider {
                     .collect::<Vec<&str>>()
                     .as_ref(),
             )?,
-            seqrepo: Rc::new(SeqRepo::new(path, &instance)?),
+            seqrepo: Arc::new(SeqRepo::new(path, &instance)?),
         })
     }
 
     /// Create a new provider allowing to inject a seqrepo.
     pub fn with_seqrepo(
         config: Config,
-        seqrepo: Rc<dyn SeqRepoInterface>,
+        seqrepo: Arc<dyn seqrepo::Interface + Sync + Send>,
     ) -> Result<Provider, Error> {
         Ok(Self {
             inner: TxProvider::with_config(
@@ -93,7 +93,7 @@ impl Provider {
     }
 }
 
-impl ProviderInterface for Provider {
+impl interface::Provider for Provider {
     fn data_version(&self) -> &str {
         self.inner.data_version()
     }
@@ -699,7 +699,7 @@ pub static REQUIRED_VERSION: &str = "1.1";
 /// The alignment method returned for all cdot transcripts.
 pub static NCBI_ALN_METHOD: &str = "splign";
 
-/// Implementation for `ProviderInterface`.
+/// Implementation for `interface::Provider`.
 impl TxProvider {
     fn data_version(&self) -> &str {
         REQUIRED_VERSION
@@ -1024,12 +1024,12 @@ impl TxProvider {
 #[cfg(test)]
 pub mod test_helpers {
     use anyhow::Error;
-    use std::rc::Rc;
+    use std::sync::Arc;
 
     use crate::data::uta_sr::test_helpers::build_writing_sr;
 
     use super::{Config, Provider};
-    use seqrepo::{CacheReadingSeqRepo, Interface as SeqRepoInterface};
+    use seqrepo;
 
     pub fn build_provider() -> Result<Provider, Error> {
         let sr_cache_mode = std::env::var("TEST_SEQREPO_CACHE_MODE")
@@ -1040,8 +1040,8 @@ pub mod test_helpers {
         log::debug!("building provider...");
         let seqrepo = if sr_cache_mode == "read" {
             log::debug!("reading provider...");
-            let seqrepo: Rc<dyn SeqRepoInterface> =
-                Rc::new(CacheReadingSeqRepo::new(sr_cache_path)?);
+            let seqrepo: Arc<dyn seqrepo::Interface + Send + Sync> =
+                Arc::new(seqrepo::CacheReadingSeqRepo::new(sr_cache_path)?);
             log::debug!("construction done...");
             seqrepo
         } else if sr_cache_mode == "write" {
@@ -1066,8 +1066,9 @@ pub mod test_helpers {
 #[cfg(test)]
 pub mod tests {
     use anyhow::Error;
-    use std::rc::Rc;
+
     use std::str::FromStr;
+    use std::sync::Arc;
 
     use chrono::NaiveDateTime;
     use pretty_assertions::assert_eq;
@@ -1076,13 +1077,19 @@ pub mod tests {
     use super::models::{gap_to_cigar, Container};
     use super::test_helpers::build_provider;
     use crate::data::interface::{
-        GeneInfoRecord, Provider as ProviderInterface, TxExonsRecord, TxForRegionRecord,
-        TxInfoRecord, TxMappingOptionsRecord, TxSimilarityRecord,
+        GeneInfoRecord, Provider, TxExonsRecord, TxForRegionRecord, TxInfoRecord,
+        TxMappingOptionsRecord, TxSimilarityRecord,
     };
-    use crate::mapper::assembly::{Config as AssemblyMapperConfig, Mapper};
+    use crate::mapper::assembly::{self, Mapper};
     use crate::parser::HgvsVariant;
     use crate::static_data::Assembly;
 
+    #[test]
+    fn test_sync() {
+        fn is_sync<T: Sync>() {}
+        is_sync::<super::Provider>();
+    }
+
     #[test]
     fn deserialize_brca1() -> Result<(), Error> {
         let json = std::fs::read_to_string(
@@ -2152,8 +2159,8 @@ pub mod tests {
     }
 
     fn build_mapper_37(normalize: bool) -> Result<Mapper, Error> {
-        let provider = Rc::new(build_provider()?);
-        let config = AssemblyMapperConfig {
+        let provider = Arc::new(build_provider()?);
+        let config = assembly::Config {
             assembly: Assembly::Grch37,
             normalize,
             ..Default::default()
diff --git a/src/data/uta.rs b/src/data/uta.rs
index d40ae19..e9d7657 100644
--- a/src/data/uta.rs
+++ b/src/data/uta.rs
@@ -12,9 +12,9 @@ use crate::sequences::seq_md5;
 use crate::static_data::{Assembly, ASSEMBLY_INFOS};
 
 use crate::data::{
-    error::Error, interface::GeneInfoRecord, interface::Provider as ProviderInterface,
-    interface::TxExonsRecord, interface::TxForRegionRecord, interface::TxIdentityInfo,
-    interface::TxInfoRecord, interface::TxMappingOptionsRecord, interface::TxSimilarityRecord,
+    error::Error, interface, interface::GeneInfoRecord, interface::TxExonsRecord,
+    interface::TxForRegionRecord, interface::TxIdentityInfo, interface::TxInfoRecord,
+    interface::TxMappingOptionsRecord, interface::TxSimilarityRecord,
 };
 
 /// Configuration for the `data::uta::Provider`.
@@ -234,7 +234,7 @@ impl Provider {
     }
 }
 
-impl ProviderInterface for Provider {
+impl interface::Provider for Provider {
     fn data_version(&self) -> &str {
         &self.config.db_schema
     }
@@ -604,11 +604,17 @@ impl ProviderInterface for Provider {
 
 #[cfg(test)]
 mod test {
-    use crate::{data::interface::Provider as ProviderInterface, static_data::Assembly};
+    use crate::{data::interface::Provider as InterfaceProvider, static_data::Assembly};
     use anyhow::Error;
 
     use super::{Config, Provider};
 
+    #[test]
+    fn test_sync() {
+        fn is_sync<T: Sync>() {}
+        is_sync::<super::Provider>();
+    }
+
     fn get_config() -> Config {
         Config {
             db_url: std::env::var("TEST_UTA_DATABASE_URL")
diff --git a/src/data/uta_sr.rs b/src/data/uta_sr.rs
index b2787ba..f12fcea 100644
--- a/src/data/uta_sr.rs
+++ b/src/data/uta_sr.rs
@@ -5,15 +5,15 @@
 //! * https://github.com/bihealth/seqrepo-rs
 
 use std::path::PathBuf;
-use std::rc::Rc;
+use std::sync::Arc;
 
-use crate::data::uta::{Config as UtaConfig, Provider as UtaProvider};
+use crate::data::uta;
 use crate::data::{
-    error::Error, interface::GeneInfoRecord, interface::Provider as ProviderInterface,
-    interface::TxExonsRecord, interface::TxForRegionRecord, interface::TxIdentityInfo,
-    interface::TxInfoRecord, interface::TxMappingOptionsRecord, interface::TxSimilarityRecord,
+    error::Error, interface, interface::GeneInfoRecord, interface::TxExonsRecord,
+    interface::TxForRegionRecord, interface::TxIdentityInfo, interface::TxInfoRecord,
+    interface::TxMappingOptionsRecord, interface::TxSimilarityRecord,
 };
-use seqrepo::{AliasOrSeqId, Interface as SeqRepoInterface, SeqRepo};
+use seqrepo::{self, AliasOrSeqId, SeqRepo};
 
 /// Configuration for the `data::uta_sr::Provider`.
 #[derive(Debug, PartialEq, Clone)]
@@ -33,8 +33,8 @@ pub struct Config {
 /// Transcripts from a UTA Postgres database, sequences comes from a SeqRepo.  This makes
 /// genome contig information available in contrast to `data::uta::Provider`.
 pub struct Provider {
-    inner: UtaProvider,
-    seqrepo: Rc<dyn SeqRepoInterface>,
+    inner: uta::Provider,
+    seqrepo: Arc<dyn seqrepo::Interface + Send + Sync>,
 }
 
 impl Provider {
@@ -58,21 +58,21 @@ impl Provider {
             .to_string();
 
         Ok(Self {
-            inner: UtaProvider::with_config(&UtaConfig {
+            inner: uta::Provider::with_config(&uta::Config {
                 db_url: config.db_url.clone(),
                 db_schema: config.db_schema,
             })?,
-            seqrepo: Rc::new(SeqRepo::new(path, &instance)?),
+            seqrepo: Arc::new(SeqRepo::new(path, &instance)?),
         })
     }
 
     /// Create a new provider allowing to inject a seqrepo.
     pub fn with_seqrepo(
         config: Config,
-        seqrepo: Rc<dyn SeqRepoInterface>,
+        seqrepo: Arc<dyn seqrepo::Interface + Send + Sync>,
     ) -> Result<Provider, Error> {
         Ok(Self {
-            inner: UtaProvider::with_config(&UtaConfig {
+            inner: uta::Provider::with_config(&uta::Config {
                 db_url: config.db_url.clone(),
                 db_schema: config.db_schema,
             })?,
@@ -81,7 +81,7 @@ impl Provider {
     }
 }
 
-impl ProviderInterface for Provider {
+impl interface::Provider for Provider {
     fn data_version(&self) -> &str {
         self.inner.data_version()
     }
@@ -174,18 +174,23 @@ impl ProviderInterface for Provider {
 #[cfg(test)]
 pub mod test_helpers {
     use anyhow::Error;
-    use std::{path::PathBuf, rc::Rc};
+    use seqrepo::{CacheReadingSeqRepo, CacheWritingSeqRepo, SeqRepo};
+    use std::{path::PathBuf, sync::Arc};
 
-    use seqrepo::{
-        CacheReadingSeqRepo, CacheWritingSeqRepo, Interface as SeqRepoInterface, SeqRepo,
-    };
+    use crate::data::interface;
 
-    use super::{Config, Provider, ProviderInterface};
+    use super::{Config, Provider};
+
+    #[test]
+    fn test_sync() {
+        fn is_sync<T: Sync>() {}
+        is_sync::<super::Provider>();
+    }
 
     /// Setup a UTA Provider with data source depending on environment variables.
     ///
     /// See README.md for information on environment variable setup.
-    pub fn build_provider() -> Result<Rc<dyn ProviderInterface>, Error> {
+    pub fn build_provider() -> Result<Arc<dyn interface::Provider + Send + Sync>, Error> {
         log::debug!("building provider...");
         let db_url = std::env::var("TEST_UTA_DATABASE_URL")
             .expect("Environment variable TEST_UTA_DATABASE_URL undefined!");
@@ -198,8 +203,8 @@ pub mod test_helpers {
 
         let (seqrepo, seqrepo_path) = if sr_cache_mode == "read" {
             log::debug!("reading provider...");
-            let seqrepo: Rc<dyn SeqRepoInterface> =
-                Rc::new(CacheReadingSeqRepo::new(sr_cache_path)?);
+            let seqrepo: Arc<dyn seqrepo::Interface + Send + Sync> =
+                Arc::new(CacheReadingSeqRepo::new(sr_cache_path)?);
             log::debug!("construction done...");
             (seqrepo, "".to_string())
         } else if sr_cache_mode == "write" {
@@ -210,7 +215,7 @@ pub mod test_helpers {
         };
         log::debug!("now returning provider...");
 
-        Ok(Rc::new(Provider::with_seqrepo(
+        Ok(Arc::new(Provider::with_seqrepo(
             Config {
                 db_url,
                 db_schema,
@@ -223,7 +228,7 @@ pub mod test_helpers {
     /// Helper that builds the cache writing SeqRepo with inner stock SeqRepo.
     pub fn build_writing_sr(
         sr_cache_path: String,
-    ) -> Result<(Rc<dyn SeqRepoInterface>, String), Error> {
+    ) -> Result<(Arc<dyn seqrepo::Interface + Send + Sync>, String), Error> {
         let seqrepo_path = std::env::var("TEST_SEQREPO_PATH")
             .expect("Environment variable TEST_SEQREPO_PATH undefined!");
         let path_buf = PathBuf::from(seqrepo_path.clone());
@@ -245,10 +250,9 @@ pub mod test_helpers {
             .to_str()
             .expect("problem with path to string conversion")
             .to_string();
-        let seqrepo: Rc<dyn SeqRepoInterface> = Rc::new(CacheWritingSeqRepo::new(
-            SeqRepo::new(path, &instance)?,
-            sr_cache_path,
-        )?);
+        let seqrepo: Arc<dyn seqrepo::Interface + Send + Sync> = Arc::new(
+            CacheWritingSeqRepo::new(SeqRepo::new(path, &instance)?, sr_cache_path)?,
+        );
         Ok((seqrepo, seqrepo_path))
     }
 }
diff --git a/src/mapper/alignment.rs b/src/mapper/alignment.rs
index d442671..3456b76 100644
--- a/src/mapper/alignment.rs
+++ b/src/mapper/alignment.rs
@@ -22,7 +22,7 @@
 //    n.        -2    -1  !  1     2     3     4     5     6     7     8     9
 //    g.   ... 123   124   125   126   127   128   129   130   131   132   133 ...
 
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::{
     data::interface::{Provider, TxExonsRecord},
@@ -119,7 +119,7 @@ pub struct Mapper {
     /// Configuration for alignment mapping.
     pub config: Config,
     /// Data provider to use for the mapping.
-    pub provider: Rc<dyn Provider>,
+    pub provider: Arc<dyn Provider + Sync + Send>,
 
     /// The transcript accession.
     pub tx_ac: String,
@@ -138,7 +138,7 @@ pub struct Mapper {
 impl Mapper {
     pub fn new(
         config: &Config,
-        provider: Rc<dyn Provider>,
+        provider: Arc<dyn Provider + Send + Sync>,
         tx_ac: &str,
         alt_ac: &str,
         alt_aln_method: &str,
@@ -499,6 +499,12 @@ mod test {
 
     use super::{build_tx_cigar, none_if_default, Mapper};
 
+    #[test]
+    fn test_sync() {
+        fn is_sync<T: Sync>() {}
+        is_sync::<super::Mapper>();
+    }
+
     #[test]
     fn build_tx_cigar_empty() {
         assert!(build_tx_cigar(&Vec::new(), 1).is_err());
diff --git a/src/mapper/altseq.rs b/src/mapper/altseq.rs
index 3a0036c..0ad9585 100644
--- a/src/mapper/altseq.rs
+++ b/src/mapper/altseq.rs
@@ -1,6 +1,6 @@
 //! Code for building alternative sequence and convertion to HGVS.p.
 
-use std::{cmp::Ordering, rc::Rc};
+use std::{cmp::Ordering, sync::Arc};
 
 use crate::{
     data::interface::Provider,
@@ -35,7 +35,7 @@ impl RefTranscriptData {
     /// * `tx_ac` -- Transcript accession.
     /// * `pro_ac` -- Protein accession.
     pub fn new(
-        provider: Rc<dyn Provider>,
+        provider: Arc<dyn Provider + Send + Sync>,
         tx_ac: &str,
         pro_ac: Option<&str>,
     ) -> Result<Self, Error> {
diff --git a/src/mapper/assembly.rs b/src/mapper/assembly.rs
index 1448a01..586b32b 100644
--- a/src/mapper/assembly.rs
+++ b/src/mapper/assembly.rs
@@ -2,10 +2,11 @@
 
 use std::collections::{HashMap, HashSet};
 use std::ops::Range;
-use std::rc::Rc;
+
+use std::sync::Arc;
 
 use crate::mapper::error::Error;
-use crate::mapper::variant::{Config as VariantMapperConfig, Mapper as VariantMapper};
+use crate::mapper::variant;
 use crate::parser::HgvsVariant;
 use crate::{data::interface::Provider, static_data::Assembly, validator::ValidationLevel};
 
@@ -68,7 +69,7 @@ impl Default for Config {
 /// Provides simplified variant mapping for a single assembly and transcript-reference
 /// alignment method.
 ///
-/// `AssemblyMapper` uses `VariantMapper`, to provide all projection functionality, and add:
+/// `AssemblyMapper` uses `variant::Mapper`, to provide all projection functionality, and add:
 ///
 /// * Automatic selection of genomic sequence accession
 /// * Transcript selection from genomic coordinates
@@ -76,7 +77,7 @@ impl Default for Config {
 /// * Special handling for PAR regions
 ///
 /// `AssemblyMapper` is instantiated with an assembly name and `alt_aln_method`. These enable
-/// the following conveniences over `VariantMapper`:
+/// the following conveniences over `variant::Mapper`:
 ///
 /// * The assembly and alignment method are used to automatically select an appropriate
 ///   chromosomal reference sequence when mapping from a transcript to a genome (i.e.,
@@ -90,8 +91,8 @@ impl Default for Config {
 /// not support contigs or other genomic sequences (e.g., NT_167249.1).
 pub struct Mapper {
     config: Config,
-    provider: Rc<dyn Provider>,
-    inner: VariantMapper,
+    provider: Arc<dyn Provider + Send + Sync>,
+    inner: variant::Mapper,
     /// Accessions of contigs in assembly.
     asm_accessions: HashSet<String>,
     /// Map from accession to contig name.
@@ -100,8 +101,8 @@ pub struct Mapper {
 
 impl Mapper {
     /// Construct new assembly mapper from config and provider.
-    pub fn new(config: Config, provider: Rc<dyn Provider>) -> Self {
-        let inner_config = VariantMapperConfig {
+    pub fn new(config: Config, provider: Arc<dyn Provider + Send + Sync>) -> Self {
+        let inner_config = variant::Config {
             replace_reference: config.replace_reference,
             strict_validation: config.strict_validation,
             prevalidation_level: config.prevalidation_level,
@@ -110,7 +111,7 @@ impl Mapper {
             renormalize_g: config.renormalize_g,
             genome_seq_available: config.genome_seq_available,
         };
-        let inner = VariantMapper::new(&inner_config, provider.clone());
+        let inner = variant::Mapper::new(&inner_config, provider.clone());
         let asm_accessions = provider
             .as_ref()
             .get_assembly_map(config.assembly)
@@ -377,6 +378,12 @@ mod test {
 
     use super::{Config, Mapper};
 
+    #[test]
+    fn test_sync() {
+        fn is_sync<T: Sync>() {}
+        is_sync::<super::Mapper>();
+    }
+
     fn build_mapper_38(normalize: bool) -> Result<Mapper, Error> {
         let provider = build_provider()?;
         let config = Config {
@@ -403,8 +410,8 @@ mod test {
         Ok(())
     }
 
-    /// The following is a port of `Test_VariantMapper` in
-    /// `test_hgvs_variantmapper_near_discrepancies.py` (sic!)
+    /// The following is a port of `Test_variant::Mapper` in
+    /// `test_hgvs_variant::Mapper_near_discrepancies.py` (sic!)
     mod cases {
         use anyhow::Error;
         use std::str::FromStr;
@@ -605,7 +612,7 @@ mod test {
     }
 
     /// The following is a port of the `Test_RefReplacement` in
-    /// `test_hgvs_variantmapper_near_discrepancies.py` (sic!)
+    /// `test_hgvs_variant::Mapper_near_discrepancies.py` (sic!)
     mod ref_replacement {
         use anyhow::Error;
         use std::str::FromStr;
@@ -864,7 +871,7 @@ mod test {
     }
 
     /// The following is a port of `Test_AssemblyMapper` in
-    /// `test_hgvs_variantmapper_near_discrepancies.py` (sic!)
+    /// `test_hgvs_variant::Mapper_near_discrepancies.py` (sic!)
     mod projections {
         use anyhow::Error;
         use std::str::FromStr;
@@ -930,7 +937,7 @@ mod test {
         }
     }
 
-    /// The following is a port of the `test_hgvs_variantmapper_near_discrepancies.py` (sic!)
+    /// The following is a port of the `test_hgvs_variant::Mapper_near_discrepancies.py` (sic!)
     mod near_discrepancies {
         use anyhow::Error;
         use std::str::FromStr;
diff --git a/src/mapper/variant.rs b/src/mapper/variant.rs
index 4128140..a57b44e 100644
--- a/src/mapper/variant.rs
+++ b/src/mapper/variant.rs
@@ -1,14 +1,14 @@
 //! Code for mapping variants between sequences.
 
-use std::{ops::Range, rc::Rc};
+use std::{ops::Range, sync::Arc};
 
 use log::{debug, info};
 
-use super::alignment::{Config as AlignmentConfig, Mapper as AlignmentMapper};
+use super::alignment;
 use crate::{
     data::interface::Provider,
     mapper::Error,
-    normalizer::{self, Config as NormalizerConfig, Normalizer},
+    normalizer::{self, Normalizer},
     parser::{
         Accession, CdsInterval, CdsLocEdit, CdsPos, GeneSymbol, GenomeInterval, GenomeLocEdit,
         HgvsVariant, Mu, NaEdit, TxInterval, TxLocEdit, TxPos,
@@ -53,8 +53,8 @@ impl Default for Config {
 /// Projects variants between sequences using `alignment::Mapper`.
 pub struct Mapper {
     config: Config,
-    provider: Rc<dyn Provider>,
-    validator: Rc<dyn Validator>,
+    provider: Arc<dyn Provider + Send + Sync>,
+    validator: Arc<dyn Validator + Send + Sync>,
 }
 
 /// Maps SequenceVariant objects between g., n., r., c., and p. representations.
@@ -91,7 +91,7 @@ pub struct Mapper {
 /// differences. For example, c_to_g accounts for the transcription
 /// start site offset, then calls n_to_g.
 impl Mapper {
-    pub fn new(config: &Config, provider: Rc<dyn Provider>) -> Mapper {
+    pub fn new(config: &Config, provider: Arc<dyn Provider + Send + Sync>) -> Mapper {
         let validator = config
             .prevalidation_level
             .validator(config.strict_validation, provider.clone());
@@ -110,7 +110,7 @@ impl Mapper {
     }
 
     /// Return a copy of the internal provider.
-    pub fn provider(&self) -> Rc<dyn Provider> {
+    pub fn provider(&self) -> Arc<dyn Provider + Send + Sync> {
         self.provider.clone()
     }
 
@@ -120,10 +120,10 @@ impl Mapper {
         tx_ac: &str,
         alt_ac: &str,
         alt_aln_method: &str,
-    ) -> Result<AlignmentMapper, Error> {
+    ) -> Result<alignment::Mapper, Error> {
         // TODO: implement caching
-        AlignmentMapper::new(
-            &AlignmentConfig {
+        alignment::Mapper::new(
+            &alignment::Config {
                 strict_bounds: self.config.strict_bounds,
             },
             self.provider.clone(),
@@ -139,7 +139,7 @@ impl Mapper {
             self,
             self.provider.clone(),
             self.validator.clone(),
-            NormalizerConfig {
+            normalizer::Config {
                 replace_reference: self.config.replace_reference,
                 ..Default::default()
             },
@@ -959,6 +959,12 @@ mod test {
 
     use super::{Config, Mapper};
 
+    #[test]
+    fn test_sync() {
+        fn is_sync<T: Sync>() {}
+        is_sync::<super::Mapper>();
+    }
+
     fn build_mapper() -> Result<Mapper, Error> {
         let provider = build_provider()?;
         let config = Config::default();
@@ -1085,10 +1091,10 @@ mod test {
         use anyhow::Error;
         use std::{
             path::{Path, PathBuf},
-            rc::Rc,
+            sync::Arc,
         };
 
-        use crate::data::interface::Provider as ProviderInterface;
+        use crate::data::interface;
         use crate::{
             data::interface::TxIdentityInfo,
             mapper::variant::{Config, Mapper},
@@ -1122,7 +1128,7 @@ mod test {
             }
         }
 
-        impl ProviderInterface for Provider {
+        impl interface::Provider for Provider {
             fn data_version(&self) -> &str {
                 panic!("for test use only");
             }
@@ -1264,7 +1270,7 @@ mod test {
 
         pub fn build_mapper(strict_bounds: bool) -> Result<Mapper, Error> {
             let path = PathBuf::from("tests/data/mapper/sanity_cp.tsv");
-            let provider = Rc::new(Provider::new(&path)?);
+            let provider = Arc::new(Provider::new(&path)?);
             let config = Config {
                 strict_bounds,
                 ..Default::default()
diff --git a/src/normalizer.rs b/src/normalizer.rs
index a02a398..34faa72 100644
--- a/src/normalizer.rs
+++ b/src/normalizer.rs
@@ -1,11 +1,11 @@
 //! Variant normalization.
 
-use std::{cmp::Ordering, ops::Range, rc::Rc};
+use std::{cmp::Ordering, ops::Range, sync::Arc};
 
 pub use crate::normalizer::error::Error;
 use crate::{
     data::interface::Provider,
-    mapper::variant::Mapper as VariantMapper,
+    mapper::variant,
     parser::{
         GenomeInterval, GenomeLocEdit, HgvsVariant, MtInterval, MtLocEdit, Mu, NaEdit, RnaInterval,
         RnaLocEdit, RnaPos, TxInterval, TxLocEdit, TxPos,
@@ -87,10 +87,10 @@ impl Default for Config {
 
 /// Normalizes variants (5' and 3' shifting).
 pub struct Normalizer<'a> {
-    pub provider: Rc<dyn Provider>,
-    pub validator: Rc<dyn Validator>,
+    pub provider: Arc<dyn Provider + Send + Sync>,
+    pub validator: Arc<dyn Validator + Send + Sync>,
     pub config: Config,
-    pub mapper: &'a VariantMapper,
+    pub mapper: &'a variant::Mapper,
 }
 
 /// Helper type used in `Normalizer::check_and_guard()`.
@@ -102,9 +102,9 @@ struct CheckAndGuardResult {
 
 impl<'a> Normalizer<'a> {
     pub fn new(
-        mapper: &'a VariantMapper,
-        provider: Rc<dyn Provider>,
-        validator: Rc<dyn Validator>,
+        mapper: &'a variant::Mapper,
+        provider: Arc<dyn Provider + Send + Sync>,
+        validator: Arc<dyn Validator + Send + Sync>,
         config: Config,
     ) -> Self {
         Self {
@@ -1043,7 +1043,7 @@ mod test {
     use test_log::test;
 
     use anyhow::Error;
-    use std::{rc::Rc, str::FromStr};
+    use std::{str::FromStr, sync::Arc};
 
     use pretty_assertions::assert_eq;
 
@@ -1055,11 +1055,17 @@ mod test {
         validator::IntrinsicValidator,
     };
 
+    #[test]
+    fn test_sync() {
+        fn is_sync<T: Sync>() {}
+        is_sync::<Normalizer>();
+    }
+
     fn normalizers(
         mapper: &Mapper,
     ) -> Result<(Normalizer, Normalizer, Normalizer, Normalizer), Error> {
         let provider = mapper.provider();
-        let validator = Rc::new(IntrinsicValidator::new(true));
+        let validator = Arc::new(IntrinsicValidator::new(true));
 
         Ok((
             Normalizer::new(
diff --git a/src/static_data/mod.rs b/src/static_data/mod.rs
index 8c43d88..11b5282 100644
--- a/src/static_data/mod.rs
+++ b/src/static_data/mod.rs
@@ -10,7 +10,7 @@ const GRCH37_JSON_GZ: &[u8] = include_bytes!("_data/GRCh37.json.gz");
 const GRCH37_P10_JSON_GZ: &[u8] = include_bytes!("_data/GRCh37.p10.json.gz");
 const GRCH38_JSON_GZ: &[u8] = include_bytes!("_data/GRCh38.json.gz");
 
-#[derive(Debug, Deserialize, Enum, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Deserialize, Enum, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum Assembly {
     Grch37,
     Grch37p10,
diff --git a/src/validator/mod.rs b/src/validator/mod.rs
index 9f273ea..81e6a77 100644
--- a/src/validator/mod.rs
+++ b/src/validator/mod.rs
@@ -2,7 +2,7 @@
 
 mod error;
 
-use std::rc::Rc;
+use std::sync::Arc;
 
 use log::{error, warn};
 
@@ -30,11 +30,15 @@ pub enum ValidationLevel {
 }
 
 impl ValidationLevel {
-    pub fn validator(&self, strict: bool, provider: Rc<dyn Provider>) -> Rc<dyn Validator> {
+    pub fn validator(
+        &self,
+        strict: bool,
+        provider: Arc<dyn Provider + Send + Sync>,
+    ) -> Arc<dyn Validator + Send + Sync> {
         match self {
-            ValidationLevel::Null => Rc::new(NullValidator::new()),
-            ValidationLevel::Intrinsic => Rc::new(IntrinsicValidator::new(strict)),
-            ValidationLevel::Full => Rc::new(FullValidator::new(strict, provider)),
+            ValidationLevel::Null => Arc::new(NullValidator::new()),
+            ValidationLevel::Intrinsic => Arc::new(IntrinsicValidator::new(strict)),
+            ValidationLevel::Full => Arc::new(FullValidator::new(strict, provider)),
         }
     }
 }
@@ -121,7 +125,7 @@ pub struct ExtrinsicValidator {
 }
 
 impl ExtrinsicValidator {
-    pub fn new(strict: bool, provider: Rc<dyn Provider>) -> Self {
+    pub fn new(strict: bool, provider: Arc<dyn Provider + Send + Sync>) -> Self {
         let config = Config {
             replace_reference: false,
             strict_validation: false,
@@ -211,7 +215,7 @@ pub struct FullValidator {
 }
 
 impl FullValidator {
-    pub fn new(strict: bool, provider: Rc<dyn Provider>) -> Self {
+    pub fn new(strict: bool, provider: Arc<dyn Provider + Send + Sync>) -> Self {
         Self {
             intrinsic: IntrinsicValidator::new(strict),
             extrinsic: ExtrinsicValidator::new(strict, provider),