diff --git a/Cargo.lock b/Cargo.lock
index 3406f64..ef150b1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,6 +1,6 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "addr2line"
@@ -119,9 +119,9 @@ dependencies = [
 
 [[package]]
 name = "async-trait"
-version = "0.1.81"
+version = "0.1.83"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6e0c28dcc82d7c8ead5cb13beb15405b57b8546e93215673ff8ca0349a028107"
+checksum = "721cae7de5c34fbb2acd27e21e6d2cf7b886dce0c27388d46c4e6c47ea4318dd"
 dependencies = [
  "proc-macro2",
  "quote",
diff --git a/src/app.rs b/src/app.rs
index ee948bf..d8ae6e8 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -21,7 +21,7 @@ use tracing::{info, info_span, Span};
 
 use crate::config::{Config, StyleConfig};
 use crate::error::{AppError, AppResult};
-use crate::post::{MarkdownPosts, PostManager, PostMetadata, RenderStats, ReturnedPost};
+use crate::post::{Filter, PostManager, PostMetadata, RenderStats, ReturnedPost};
 use crate::serve_dir_included::handle;
 
 const STATIC: Dir<'static> = include_dir!("$CARGO_MANIFEST_DIR/static");
@@ -43,8 +43,8 @@ const BINGUS_INFO: BingusInfo = BingusInfo {
 #[non_exhaustive]
 pub struct AppState {
     pub config: Arc<Config>,
-    pub posts: Arc<MarkdownPosts<Arc<Config>>>,
-    pub reg: Arc<RwLock<Handlebars<'static>>>,
+    pub posts: Arc<dyn PostManager + Send + Sync>,
+    pub templates: Arc<RwLock<Handlebars<'static>>>,
 }
 
 #[derive(Serialize)]
@@ -120,14 +120,17 @@ fn join_tags_for_meta(tags: &Map<String, serde_json::Value>, delim: &str) -> Str
     s
 }
 
-async fn index<'a>(
+async fn index(
     State(AppState {
-        config, posts, reg, ..
+        config,
+        posts,
+        templates: reg,
+        ..
     }): State<AppState>,
     Query(query): Query<QueryParams>,
 ) -> AppResult<impl IntoResponse> {
     let posts = posts
-        .get_max_n_post_metadata_with_optional_tag_sorted(query.num_posts, query.tag.as_ref())
+        .get_max_n_post_metadata_with_optional_tag_sorted(query.num_posts, query.tag.as_deref())
         .await?;
 
     let tags = collect_tags(&posts);
@@ -157,7 +160,7 @@ async fn all_posts(
     Query(query): Query<QueryParams>,
 ) -> AppResult<Json<Vec<PostMetadata>>> {
     let posts = posts
-        .get_max_n_post_metadata_with_optional_tag_sorted(query.num_posts, query.tag.as_ref())
+        .get_max_n_post_metadata_with_optional_tag_sorted(query.num_posts, query.tag.as_deref())
         .await?;
 
     Ok(Json(posts))
@@ -172,11 +175,13 @@ async fn rss(
     }
 
     let posts = posts
-        .get_all_posts(|metadata, _| {
+        .get_all_posts(
             query
                 .tag
-                .as_ref().is_none_or(|tag| metadata.tags.contains(tag))
-        })
+                .as_ref()
+                .and(Some(Filter::Tags(query.tag.as_deref().as_slice())))
+                .as_slice(),
+        )
         .await?;
 
     let mut channel = ChannelBuilder::default();
@@ -223,7 +228,10 @@ async fn rss(
 
 async fn post(
     State(AppState {
-        config, posts, reg, ..
+        config,
+        posts,
+        templates: reg,
+        ..
     }): State<AppState>,
     Path(name): Path<String>,
 ) -> AppResult<impl IntoResponse> {
diff --git a/src/main.rs b/src/main.rs
index e9627aa..f671d93 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -31,6 +31,7 @@ use tracing_subscriber::layer::SubscriberExt;
 use tracing_subscriber::{util::SubscriberInitExt, EnvFilter};
 
 use crate::app::AppState;
+use crate::post::cache::{load_cache, CacheGuard, CACHE_VERSION};
 use crate::post::{MarkdownPosts, PostManager};
 use crate::templates::new_registry;
 use crate::templates::watcher::watch_templates;
@@ -87,7 +88,31 @@ async fn main() -> eyre::Result<()> {
         .instrument(info_span!("custom_template_watcher")),
     );
 
-    let posts = Arc::new(MarkdownPosts::new(Arc::clone(&config)).await?);
+    let cache = if config.cache.enable {
+        if config.cache.persistence && tokio::fs::try_exists(&config.cache.file).await? {
+            info!("loading cache from file");
+            let mut cache = load_cache(&config.cache).await.unwrap_or_else(|err| {
+                error!("failed to load cache: {}", err);
+                info!("using empty cache");
+                Default::default()
+            });
+
+            if cache.version() < CACHE_VERSION {
+                warn!("cache version changed, clearing cache");
+                cache = Default::default();
+            };
+
+            Some(cache)
+        } else {
+            Some(Default::default())
+        }
+    } else {
+        None
+    }
+    .map(|cache| CacheGuard::new(cache, config.cache.clone()))
+    .map(Arc::new);
+
+    let posts = Arc::new(MarkdownPosts::new(Arc::clone(&config), cache.clone()).await?);
 
     if config.cache.enable && config.cache.cleanup {
         if let Some(millis) = config.cache.cleanup_interval {
@@ -112,8 +137,8 @@ async fn main() -> eyre::Result<()> {
 
     let state = AppState {
         config: Arc::clone(&config),
-        posts: Arc::clone(&posts),
-        reg: Arc::clone(&reg),
+        posts: posts as Arc<dyn PostManager + Send + Sync>,
+        templates: Arc::clone(&reg),
     };
     let app = app::new(&config).with_state(state.clone());
 
diff --git a/src/post/cache.rs b/src/post/cache.rs
index cd3e837..250a073 100644
--- a/src/post/cache.rs
+++ b/src/post/cache.rs
@@ -1,13 +1,13 @@
-use std::hash::{DefaultHasher, Hash, Hasher};
-use std::io::Read;
+use std::io::{Read, Write};
+use std::ops::Deref;
 
-use crate::config::{Config, RenderConfig};
+use crate::config::CacheConfig;
 use crate::post::PostMetadata;
 use color_eyre::eyre::{self, Context};
 use scc::HashMap;
 use serde::{Deserialize, Serialize};
 use tokio::io::AsyncReadExt;
-use tracing::{debug, instrument};
+use tracing::{debug, info, instrument};
 
 /// do not persist cache if this version number changed
 pub const CACHE_VERSION: u16 = 2;
@@ -17,34 +17,24 @@ pub struct CacheValue {
     pub metadata: PostMetadata,
     pub rendered: String,
     pub mtime: u64,
-    config_hash: u64,
+    extra: u64,
 }
 
 #[derive(Serialize, Deserialize, Clone)]
-pub struct Cache(HashMap<String, CacheValue>, u16);
+pub struct FileCache(HashMap<String, CacheValue>, u16);
 
-impl Default for Cache {
+impl Default for FileCache {
     fn default() -> Self {
         Self(Default::default(), CACHE_VERSION)
     }
 }
 
-impl Cache {
-    pub async fn lookup(
-        &self,
-        name: &str,
-        mtime: u64,
-        config: &RenderConfig,
-    ) -> Option<CacheValue> {
+impl FileCache {
+    pub async fn lookup(&self, name: &str, mtime: u64, extra: u64) -> Option<CacheValue> {
         match self.0.get_async(name).await {
             Some(entry) => {
                 let cached = entry.get();
-                if mtime <= cached.mtime && {
-                    let mut hasher = DefaultHasher::new();
-                    config.hash(&mut hasher);
-                    hasher.finish()
-                } == cached.config_hash
-                {
+                if extra == cached.extra && mtime <= cached.mtime {
                     Some(cached.clone())
                 } else {
                     let _ = entry.remove();
@@ -76,17 +66,13 @@ impl Cache {
         metadata: PostMetadata,
         mtime: u64,
         rendered: String,
-        config: &RenderConfig,
+        extra: u64,
     ) -> Result<(), (String, (PostMetadata, String))> {
-        let mut hasher = DefaultHasher::new();
-        config.hash(&mut hasher);
-        let hash = hasher.finish();
-
         let value = CacheValue {
             metadata,
             rendered,
             mtime,
-            config_hash: hash,
+            extra,
         };
 
         if self
@@ -136,12 +122,67 @@ impl Cache {
     }
 }
 
-pub(crate) async fn load_cache(config: &Config) -> Result<Cache, eyre::Report> {
-    let path = &config.cache.file;
+pub struct CacheGuard {
+    inner: FileCache,
+    config: CacheConfig,
+}
+
+impl CacheGuard {
+    pub fn new(cache: FileCache, config: CacheConfig) -> Self {
+        Self {
+            inner: cache,
+            config,
+        }
+    }
+
+    fn try_drop(&mut self) -> Result<(), eyre::Report> {
+        // write cache to file
+        let path = &self.config.file;
+        let serialized = bitcode::serialize(&self.inner).context("failed to serialize cache")?;
+        let mut cache_file = std::fs::File::create(path)
+            .with_context(|| format!("failed to open cache at {}", path.display()))?;
+        let compression_level = self.config.compression_level;
+        if self.config.compress {
+            std::io::Write::write_all(
+                &mut zstd::stream::write::Encoder::new(cache_file, compression_level)?
+                    .auto_finish(),
+                &serialized,
+            )
+        } else {
+            cache_file.write_all(&serialized)
+        }
+        .context("failed to write cache to file")?;
+        info!("wrote cache to {}", path.display());
+        Ok(())
+    }
+}
+
+impl Deref for CacheGuard {
+    type Target = FileCache;
+
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+impl AsRef<FileCache> for CacheGuard {
+    fn as_ref(&self) -> &FileCache {
+        &self.inner
+    }
+}
+
+impl Drop for CacheGuard {
+    fn drop(&mut self) {
+        self.try_drop().expect("cache to save successfully")
+    }
+}
+
+pub(crate) async fn load_cache(config: &CacheConfig) -> Result<FileCache, eyre::Report> {
+    let path = &config.file;
     let mut cache_file = tokio::fs::File::open(&path)
         .await
         .context("failed to open cache file")?;
-    let serialized = if config.cache.compress {
+    let serialized = if config.compress {
         let cache_file = cache_file.into_std().await;
         tokio::task::spawn_blocking(move || {
             let mut buf = Vec::with_capacity(4096);
diff --git a/src/post/markdown_posts.rs b/src/post/markdown_posts.rs
index 5ef0290..50547e6 100644
--- a/src/post/markdown_posts.rs
+++ b/src/post/markdown_posts.rs
@@ -1,11 +1,13 @@
 use std::collections::BTreeSet;
-use std::io::{self, Write};
-use std::ops::Deref;
+use std::hash::{DefaultHasher, Hash, Hasher};
+use std::io;
 use std::path::Path;
+use std::sync::Arc;
 use std::time::Duration;
 use std::time::Instant;
 use std::time::SystemTime;
 
+use axum::async_trait;
 use axum::http::HeaderValue;
 use chrono::{DateTime, Utc};
 use color_eyre::eyre::{self, Context};
@@ -14,14 +16,17 @@ use fronma::parser::{parse, ParsedData};
 use serde::Deserialize;
 use tokio::fs;
 use tokio::io::AsyncReadExt;
-use tracing::{error, info, warn};
+use tracing::warn;
 
 use crate::config::Config;
 use crate::markdown_render::{build_syntect, render};
-use crate::post::cache::{load_cache, Cache, CACHE_VERSION};
-use crate::post::{PostError, PostManager, PostMetadata, RenderStats, ReturnedPost};
 use crate::systemtime_as_secs::as_secs;
 
+use super::cache::CacheGuard;
+use super::{
+    ApplyFilters, Filter, PostError, PostManager, PostMetadata, RenderStats, ReturnedPost,
+};
+
 #[derive(Deserialize)]
 struct FrontMatter {
     pub title: String,
@@ -57,48 +62,30 @@ impl FrontMatter {
         }
     }
 }
-pub struct MarkdownPosts<C>
-where
-    C: Deref<Target = Config>,
-{
-    cache: Option<Cache>,
-    config: C,
+
+pub struct MarkdownPosts {
+    cache: Option<Arc<CacheGuard>>,
+    config: Arc<Config>,
+    render_hash: u64,
     syntect: SyntectAdapter,
 }
 
-impl<C> MarkdownPosts<C>
-where
-    C: Deref<Target = Config>,
-{
-    pub async fn new(config: C) -> eyre::Result<MarkdownPosts<C>> {
+impl MarkdownPosts {
+    pub async fn new(
+        config: Arc<Config>,
+        cache: Option<Arc<CacheGuard>>,
+    ) -> eyre::Result<MarkdownPosts> {
         let syntect =
             build_syntect(&config.render).context("failed to create syntax highlighting engine")?;
 
-        let cache = if config.cache.enable {
-            if config.cache.persistence && tokio::fs::try_exists(&config.cache.file).await? {
-                info!("loading cache from file");
-                let mut cache = load_cache(&config).await.unwrap_or_else(|err| {
-                    error!("failed to load cache: {}", err);
-                    info!("using empty cache");
-                    Default::default()
-                });
-
-                if cache.version() < CACHE_VERSION {
-                    warn!("cache version changed, clearing cache");
-                    cache = Default::default();
-                };
-
-                Some(cache)
-            } else {
-                Some(Default::default())
-            }
-        } else {
-            None
-        };
+        let mut hasher = DefaultHasher::new();
+        config.render.hash(&mut hasher);
+        let render_hash = hasher.finish();
 
         Ok(Self {
             cache,
             config,
+            render_hash,
             syntect,
         })
     }
@@ -131,14 +118,14 @@ where
         let post = render(body, Some(&self.syntect));
         let rendering = before_render.elapsed();
 
-        if let Some(cache) = self.cache.as_ref() {
+        if let Some(cache) = &self.cache {
             cache
                 .insert(
                     name.to_string(),
                     metadata.clone(),
                     as_secs(&modified),
                     post.clone(),
-                    &self.config.render,
+                    self.render_hash,
                 )
                 .await
                 .unwrap_or_else(|err| warn!("failed to insert {:?} into cache", err.0))
@@ -146,55 +133,44 @@ where
 
         Ok((metadata, post, (parsing, rendering)))
     }
+}
 
-    fn cache(&self) -> Option<&Cache> {
-        self.cache.as_ref()
-    }
+#[async_trait]
+impl PostManager for MarkdownPosts {
+    async fn get_all_posts(
+        &self,
+        filters: &[Filter<'_>],
+    ) -> Result<Vec<(PostMetadata, String, RenderStats)>, PostError> {
+        let mut posts = Vec::new();
 
-    fn try_drop(&mut self) -> Result<(), eyre::Report> {
-        // write cache to file
-        let config = &self.config.cache;
-        if config.enable
-            && config.persistence
-            && let Some(cache) = self.cache()
-        {
-            let path = &config.file;
-            let serialized = bitcode::serialize(cache).context("failed to serialize cache")?;
-            let mut cache_file = std::fs::File::create(path)
-                .with_context(|| format!("failed to open cache at {}", path.display()))?;
-            let compression_level = config.compression_level;
-            if config.compress {
-                std::io::Write::write_all(
-                    &mut zstd::stream::write::Encoder::new(cache_file, compression_level)?
-                        .auto_finish(),
-                    &serialized,
-                )
-            } else {
-                cache_file.write_all(&serialized)
+        let mut read_dir = fs::read_dir(&self.config.dirs.posts).await?;
+        while let Some(entry) = read_dir.next_entry().await? {
+            let path = entry.path();
+            let stat = fs::metadata(&path).await?;
+
+            if stat.is_file() && path.extension().is_some_and(|ext| ext == "md") {
+                let name = path
+                    .clone()
+                    .file_stem()
+                    .unwrap()
+                    .to_string_lossy()
+                    .to_string();
+
+                let post = self.get_post(&name).await?;
+                if let ReturnedPost::Rendered(meta, content, stats) = post
+                    && meta.apply_filters(filters)
+                {
+                    posts.push((meta, content, stats));
+                }
             }
-            .context("failed to write cache to file")?;
-            info!("wrote cache to {}", path.display());
         }
-        Ok(())
-    }
-}
 
-impl<C> Drop for MarkdownPosts<C>
-where
-    C: Deref<Target = Config>,
-{
-    fn drop(&mut self) {
-        self.try_drop().unwrap()
+        Ok(posts)
     }
-}
 
-impl<C> PostManager for MarkdownPosts<C>
-where
-    C: Deref<Target = Config>,
-{
     async fn get_all_post_metadata(
         &self,
-        filter: impl Fn(&PostMetadata) -> bool,
+        filters: &[Filter<'_>],
     ) -> Result<Vec<PostMetadata>, PostError> {
         let mut posts = Vec::new();
 
@@ -207,15 +183,15 @@ where
                 let mtime = as_secs(&stat.modified()?);
                 let name = String::from(path.file_stem().unwrap().to_string_lossy());
 
-                if let Some(cache) = self.cache.as_ref()
+                if let Some(cache) = &self.cache
                     && let Some(hit) = cache.lookup_metadata(&name, mtime).await
-                    && filter(&hit)
+                    && hit.apply_filters(filters)
                 {
                     posts.push(hit);
                 } else {
                     match self.parse_and_render(name, path).await {
                         Ok((metadata, ..)) => {
-                            if filter(&metadata) {
+                            if metadata.apply_filters(filters) {
                                 posts.push(metadata);
                             }
                         }
@@ -235,37 +211,6 @@ where
         Ok(posts)
     }
 
-    async fn get_all_posts(
-        &self,
-        filter: impl Fn(&PostMetadata, &str) -> bool,
-    ) -> Result<Vec<(PostMetadata, String, RenderStats)>, PostError> {
-        let mut posts = Vec::new();
-
-        let mut read_dir = fs::read_dir(&self.config.dirs.posts).await?;
-        while let Some(entry) = read_dir.next_entry().await? {
-            let path = entry.path();
-            let stat = fs::metadata(&path).await?;
-
-            if stat.is_file() && path.extension().is_some_and(|ext| ext == "md") {
-                let name = path
-                    .clone()
-                    .file_stem()
-                    .unwrap()
-                    .to_string_lossy()
-                    .to_string();
-
-                let post = self.get_post(&name).await?;
-                if let ReturnedPost::Rendered(meta, content, stats) = post
-                    && filter(&meta, &content)
-                {
-                    posts.push((meta, content, stats));
-                }
-            }
-        }
-
-        Ok(posts)
-    }
-
     async fn get_post(&self, name: &str) -> Result<ReturnedPost, PostError> {
         if self.config.markdown_access && name.ends_with(".md") {
             let path = self.config.dirs.posts.join(name);
@@ -274,7 +219,7 @@ where
                 Ok(value) => value,
                 Err(err) => match err.kind() {
                     io::ErrorKind::NotFound => {
-                        if let Some(cache) = self.cache.as_ref() {
+                        if let Some(cache) = &self.cache {
                             cache.remove(name).await;
                         }
                         return Err(PostError::NotFound(name.to_string()));
@@ -299,7 +244,7 @@ where
                 Ok(value) => value,
                 Err(err) => match err.kind() {
                     io::ErrorKind::NotFound => {
-                        if let Some(cache) = self.cache.as_ref() {
+                        if let Some(cache) = &self.cache {
                             cache.remove(name).await;
                         }
                         return Err(PostError::NotFound(name.to_string()));
@@ -309,8 +254,8 @@ where
             };
             let mtime = as_secs(&stat.modified()?);
 
-            if let Some(cache) = self.cache.as_ref()
-                && let Some(hit) = cache.lookup(name, mtime, &self.config.render).await
+            if let Some(cache) = &self.cache
+                && let Some(hit) = cache.lookup(name, mtime, self.render_hash).await
             {
                 Ok(ReturnedPost::Rendered(
                     hit.metadata,
@@ -330,7 +275,7 @@ where
     }
 
     async fn cleanup(&self) {
-        if let Some(cache) = self.cache.as_ref() {
+        if let Some(cache) = &self.cache {
             cache
                 .cleanup(|name| {
                     std::fs::metadata(self.config.dirs.posts.join(name.to_owned() + ".md"))
diff --git a/src/post/mod.rs b/src/post/mod.rs
index 4ba51d4..c501746 100644
--- a/src/post/mod.rs
+++ b/src/post/mod.rs
@@ -3,7 +3,7 @@ pub mod markdown_posts;
 
 use std::time::Duration;
 
-use axum::http::HeaderValue;
+use axum::{async_trait, http::HeaderValue};
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
 
@@ -37,29 +37,58 @@ pub enum ReturnedPost {
     Raw(Vec<u8>, HeaderValue),
 }
 
+pub enum Filter<'a> {
+    Tags(&'a [&'a str]),
+}
+
+impl<'a> Filter<'a> {
+    pub fn apply(&self, meta: &PostMetadata) -> bool {
+        match self {
+            Filter::Tags(tags) => tags
+                .iter()
+                .any(|tag| meta.tags.iter().any(|meta_tag| meta_tag == tag)),
+        }
+    }
+}
+
+pub trait ApplyFilters {
+    fn apply_filters(&self, filters: &[Filter<'_>]) -> bool;
+}
+
+impl ApplyFilters for PostMetadata {
+    fn apply_filters(&self, filters: &[Filter<'_>]) -> bool {
+        for filter in filters {
+            if !filter.apply(self) {
+                return false;
+            }
+        }
+        true
+    }
+}
+
+#[async_trait]
 pub trait PostManager {
     async fn get_all_post_metadata(
         &self,
-        filter: impl Fn(&PostMetadata) -> bool,
+        filters: &[Filter<'_>],
     ) -> Result<Vec<PostMetadata>, PostError> {
-        self.get_all_posts(|m, _| filter(m))
+        self.get_all_posts(filters)
             .await
             .map(|vec| vec.into_iter().map(|(meta, ..)| meta).collect())
     }
 
     async fn get_all_posts(
         &self,
-        filter: impl Fn(&PostMetadata, &str) -> bool,
+        filters: &[Filter<'_>],
     ) -> Result<Vec<(PostMetadata, String, RenderStats)>, PostError>;
 
     async fn get_max_n_post_metadata_with_optional_tag_sorted(
         &self,
         n: Option<usize>,
-        tag: Option<&String>,
+        tag: Option<&str>,
     ) -> Result<Vec<PostMetadata>, PostError> {
-        let mut posts = self
-            .get_all_post_metadata(|metadata| tag.is_none_or(|tag| metadata.tags.contains(tag)))
-            .await?;
+        let filters = tag.and(Some(Filter::Tags(tag.as_slice())));
+        let mut posts = self.get_all_post_metadata(filters.as_slice()).await?;
         // we still want some semblance of order if created_at is None so sort by mtime as well
         posts.sort_unstable_by_key(|metadata| metadata.modified_at.unwrap_or_default());
         posts.sort_by_key(|metadata| metadata.created_at.unwrap_or_default());