From 7b2a8577a90301063985ffd5f7340a40697c8dce Mon Sep 17 00:00:00 2001
From: Dionisio <dpozo@futurespace.es>
Date: Mon, 2 Mar 2026 23:58:15 +0100
Subject: [PATCH] perf(caldav): zero-alloc iCal generation with write!()

Replace push_str(&format!(...)) pattern in generate_full_calendar_ical,
generate_event_ical, and generate_vevent with direct write!() into a
pre-sized String buffer.

Before: ~5N+1 heap allocations for N events (temporary Strings created
by format!(), copied into the main buffer, then dropped).

After: 1 allocation (the initial String::with_capacity). All write!()
calls format directly into the destination buffer with zero intermediate
Strings.
---
 Cargo.lock                                    | 287 ++++++++++++++----
 Cargo.toml                                    |  16 +-
 src/interfaces/api/handlers/caldav_handler.rs |  39 ++-
 3 files changed, 258 insertions(+), 84 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 8249d5ca..61150d9d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -55,9 +55,9 @@ checksum = "5192cca8006f1fd4f7237516f40fa183bb07f8fbdfedaa0036de5ea9b0b45e78"
 
 [[package]]
 name = "anyhow"
-version = "1.0.101"
+version = "1.0.102"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5f0e0fee31ef5ed1ba1316088939cea399010ed7731dba877ed44aeb407a75ea"
+checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
 
 [[package]]
 name = "argon2"
@@ -261,9 +261,9 @@ checksum = "2af50177e190e07a26ab74f8b1efbfe2ef87da2116221318cb1c2e82baf7de06"
 
 [[package]]
 name = "bitflags"
-version = "2.10.0"
+version = "2.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "812e12b5285cc515a9c72a5c1d3b6d46a19dac5acfef5265968c166106e31dd3"
+checksum = "843867be96c8daad0d758b57df9392b6d8d271134fce549de6ce169ff98a92af"
 dependencies = [
  "serde_core",
 ]
@@ -353,9 +353,9 @@ checksum = "1e748733b7cbc798e1434b6ac524f0c1ff2ab456fe201501e6497c8417a4fc33"
 
 [[package]]
 name = "cc"
-version = "1.2.55"
+version = "1.2.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "47b26a0954ae34af09b50f0de26458fa95369a0d478d8236d3f93082b219bd29"
+checksum = "aebf35691d1bfb0ac386a69bac2fde4dd276fb618cf8bf4f5318fe285e821bb2"
 dependencies = [
  "find-msvc-tools",
  "shlex",
@@ -386,9 +386,9 @@ checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
 
 [[package]]
 name = "chrono"
-version = "0.4.43"
+version = "0.4.44"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fac4744fb15ae8337dc853fee7fb3f4e48c0fbaa23d0afe49c447b4fab126118"
+checksum = "c673075a2e0e5f4a1dde27ce9dee1ea4558c7ffe648f576438a20ca1d2acc4b0"
 dependencies = [
  "iana-time-zone",
  "js-sys",
@@ -601,9 +601,9 @@ dependencies = [
 
 [[package]]
 name = "deranged"
-version = "0.5.5"
+version = "0.5.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ececcb659e7ba858fb4f10388c250a7252eb0a27373f1a72b8748afdd248e587"
+checksum = "cc3dc5ad92c2e2d1c193bbbbdf2ea477cb81331de4f3103f267ca18368b988c4"
 dependencies = [
  "powerfmt",
 ]
@@ -733,7 +733,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
 dependencies = [
  "libc",
- "windows-sys 0.61.2",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -865,9 +865,9 @@ dependencies = [
 
 [[package]]
 name = "futures"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "65bc07b1a8bc7c85c5f2e110c476c7389b4554ba72af57d8445ea63a576b0876"
+checksum = "8b147ee9d1f6d097cef9ce628cd2ee62288d963e16fb287bd9286455b241382d"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -880,9 +880,9 @@ dependencies = [
 
 [[package]]
 name = "futures-channel"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2dff15bf788c671c1934e366d07e30c1814a8ef514e1af724a602e8a2fbe1b10"
+checksum = "07bbe89c50d7a535e539b8c17bc0b49bdb77747034daa8087407d655f3f7cc1d"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -890,15 +890,15 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "05f29059c0c2090612e8d742178b0580d2dc940c837851ad723096f87af6663e"
+checksum = "7e3450815272ef58cec6d564423f6e755e25379b217b0bc688e295ba24df6b1d"
 
 [[package]]
 name = "futures-executor"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1e28d1d997f585e54aebc3f97d39e72338912123a67330d723fdbb564d646c9f"
+checksum = "baf29c38818342a3b26b5b923639e7b1f4a61fc5e76102d4b1981c6dc7a7579d"
 dependencies = [
  "futures-core",
  "futures-task",
@@ -918,9 +918,9 @@ dependencies = [
 
 [[package]]
 name = "futures-io"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9e5c1b78ca4aae1ac06c48a526a655760685149f0d465d21f37abfe57ce075c6"
+checksum = "cecba35d7ad927e23624b22ad55235f2239cfa44fd10428eecbeba6d6a717718"
 
 [[package]]
 name = "futures-lite"
@@ -937,9 +937,9 @@ dependencies = [
 
 [[package]]
 name = "futures-macro"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "162ee34ebcb7c64a8abebc059ce0fee27c2262618d7b60ed8faf72fef13c3650"
+checksum = "e835b70203e41293343137df5c0664546da5745f82ec9b84d40be8336958447b"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -948,21 +948,21 @@ dependencies = [
 
 [[package]]
 name = "futures-sink"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e575fab7d1e0dcb8d0c7bcf9a63ee213816ab51902e6d244a95819acacf1d4f7"
+checksum = "c39754e157331b013978ec91992bde1ac089843443c49cbc7f46150b0fad0893"
 
 [[package]]
 name = "futures-task"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f90f7dce0722e95104fcb095585910c0977252f286e354b5e3bd38902cd99988"
+checksum = "037711b3d59c33004d3856fbdc83b99d4ff37a24768fa1be9ce3538a1cde4393"
 
 [[package]]
 name = "futures-util"
-version = "0.3.31"
+version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9fa08315bb612088cc391249efdc3bc77536f16c91f6cf495e6fbe85b20a4a81"
+checksum = "389ca41296e6190b48053de0321d02a77f32f8a5d2461dd38762c0593805c6d6"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -972,7 +972,6 @@ dependencies = [
  "futures-task",
  "memchr",
  "pin-project-lite",
- "pin-utils",
  "slab",
 ]
 
@@ -1014,6 +1013,19 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "139ef39800118c7683f2fd3c98c1b23c09ae076556b435f8e9064ae108aaeeec"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi",
+ "wasip2",
+ "wasip3",
+]
+
 [[package]]
 name = "gif"
 version = "0.14.1"
@@ -1344,6 +1356,12 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "id-arena"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d3067d79b975e8844ca9eb072e16b31c3c1c36928edf9c6789548c524d0d954"
+
 [[package]]
 name = "idna"
 version = "1.1.0"
@@ -1401,6 +1419,8 @@ checksum = "7714e70437a7dc3ac8eb7e6f8df75fd8eb422675fc7678aff7364301092b1017"
 dependencies = [
  "equivalent",
  "hashbrown 0.16.1",
+ "serde",
+ "serde_core",
 ]
 
 [[package]]
@@ -1477,10 +1497,16 @@ dependencies = [
 ]
 
 [[package]]
-name = "libc"
-version = "0.2.180"
+name = "leb128fmt"
+version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bcc35a38544a891a5f7c865aca548a982ccb3b8650a5b06d0fd33a10283c56fc"
+checksum = "09edd9e8b54e49e587e4f6295a7d29c3ea94d469cb40ab8ca70b288248a81db2"
+
+[[package]]
+name = "libc"
+version = "0.2.182"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6800badb6cb2082ffd7b6a67e6125bb39f18782f793520caee8cb8846be06112"
 
 [[package]]
 name = "libm"
@@ -1521,9 +1547,9 @@ dependencies = [
 
 [[package]]
 name = "linux-raw-sys"
-version = "0.11.0"
+version = "0.12.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df1d3c3b53da64cf5760482273a98e575c651a67eec7f77df96b5b642de8f039"
+checksum = "32a66949e030da00e8c7d4434b251670a91556f4144941d37452769c25d58a53"
 
 [[package]]
 name = "litemap"
@@ -1585,9 +1611,9 @@ checksum = "ae960838283323069879657ca3de837e9f7bbb4c7bf6ea7f1b290d5e9476d2e0"
 
 [[package]]
 name = "memchr"
-version = "2.7.6"
+version = "2.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f52b00d39961fc5b2736ea853c9cc86238e165017a493d1d5c8eac6bdc4cc273"
+checksum = "f8ca58f447f06ed17d5fc4043ce1b10dd205e060fb3ce5b979b8ed8e59ff3f79"
 
 [[package]]
 name = "mimalloc"
@@ -1714,7 +1740,7 @@ version = "0.50.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7957b9740744892f114936ab4a57b3f487491bbeafaf8083688b16841a4240e5"
 dependencies = [
- "windows-sys 0.61.2",
+ "windows-sys 0.60.2",
 ]
 
 [[package]]
@@ -2057,6 +2083,16 @@ dependencies = [
  "termtree",
 ]
 
+[[package]]
+name = "prettyplease"
+version = "0.2.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "479ca8adacdd7ce8f1fb39ce9ecccbfe93a3f1344b3d0d97f20bc0196208f62b"
+dependencies = [
+ "proc-macro2",
+ "syn",
+]
+
 [[package]]
 name = "primeorder"
 version = "0.13.6"
@@ -2092,9 +2128,9 @@ checksum = "a993555f31e5a609f617c12db6250dedcac1b0a85076912c436e6fc9b2c8e6a3"
 
 [[package]]
 name = "quick-xml"
-version = "0.39.0"
+version = "0.39.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f2e3bf4aa9d243beeb01a7b3bc30b77cfe2c44e24ec02d751a7104a53c2c49a1"
+checksum = "958f21e8e7ceb5a1aa7fa87fab28e7c75976e0bfe7e23ff069e0a260f894067d"
 dependencies = [
  "memchr",
 ]
@@ -2382,15 +2418,15 @@ dependencies = [
 
 [[package]]
 name = "rustix"
-version = "1.1.3"
+version = "1.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "146c9e247ccc180c1f61615433868c99f3de3ae256a30a43b49f67c2d9171f34"
+checksum = "b6fe4565b9518b83ef4f91bb47ce29620ca828bd32cb7e408f0062e9930ba190"
 dependencies = [
  "bitflags",
  "errno",
  "libc",
  "linux-raw-sys",
- "windows-sys 0.61.2",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -2864,9 +2900,9 @@ checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
 
 [[package]]
 name = "syn"
-version = "2.0.114"
+version = "2.0.117"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d4d107df263a3013ef9b1879b0df87d706ff80f65a86ea879bd9c31f9b307c2a"
+checksum = "e665b8803e7b1d2a727f4023456bbbbe74da67099c585258af0ad9c5013b9b99"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2901,15 +2937,15 @@ checksum = "7b2093cf4c8eb1e67749a6762251bc9cd836b6fc171623bd0a9d324d37af2417"
 
 [[package]]
 name = "tempfile"
-version = "3.25.0"
+version = "3.26.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0136791f7c95b1f6dd99f9cc786b91bb81c3800b639b3478e561ddb7be95e5f1"
+checksum = "82a72c767771b47409d2345987fda8628641887d5466101319899796367354a0"
 dependencies = [
  "fastrand",
- "getrandom 0.3.4",
+ "getrandom 0.4.1",
  "once_cell",
  "rustix",
- "windows-sys 0.61.2",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -3210,9 +3246,9 @@ checksum = "5c1cb5db39152898a79168971543b1cb5020dff7fe43c8dc468b0885f5e29df5"
 
 [[package]]
 name = "unicode-ident"
-version = "1.0.22"
+version = "1.0.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9312f7c4f6ff9069b165498234ce8be658059c6728633667c526e27dc2cf1df5"
+checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
 
 [[package]]
 name = "unicode-normalization"
@@ -3229,6 +3265,12 @@ version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7df058c713841ad818f1dc5d3fd88063241cc61f49f5fbea4b951e8cf5a8d71d"
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ebc1c04c71510c7f702b52b7c350734c9ff1295c464a03335b00bb84fc54f853"
+
 [[package]]
 name = "untrusted"
 version = "0.9.0"
@@ -3255,11 +3297,11 @@ checksum = "b6c140620e7ffbb22c2dee59cafe6084a59b5ffc27a8859a5f0d494b5d52b6be"
 
 [[package]]
 name = "uuid"
-version = "1.20.0"
+version = "1.21.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ee48d38b119b0cd71fe4141b30f5ba9c7c5d9f4e7a3a8b4a674e4b6ef789976f"
+checksum = "b672338555252d43fd2240c714dc444b8c6fb0a5c5335e65a07bba7742735ddb"
 dependencies = [
- "getrandom 0.3.4",
+ "getrandom 0.4.1",
  "js-sys",
  "serde_core",
  "wasm-bindgen",
@@ -3307,6 +3349,15 @@ dependencies = [
  "wit-bindgen",
 ]
 
+[[package]]
+name = "wasip3"
+version = "0.4.0+wasi-0.3.0-rc-2026-01-06"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5428f8bf88ea5ddc08faddef2ac4a67e390b88186c703ce6dbd955e1c145aca5"
+dependencies = [
+ "wit-bindgen",
+]
+
 [[package]]
 name = "wasite"
 version = "0.1.0"
@@ -3372,6 +3423,40 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "wasm-encoder"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "990065f2fe63003fe337b932cfb5e3b80e0b4d0f5ff650e6985b1048f62c8319"
+dependencies = [
+ "leb128fmt",
+ "wasmparser",
+]
+
+[[package]]
+name = "wasm-metadata"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb0e353e6a2fbdc176932bbaab493762eb1255a7900fe0fea1a2f96c296cc909"
+dependencies = [
+ "anyhow",
+ "indexmap",
+ "wasm-encoder",
+ "wasmparser",
+]
+
+[[package]]
+name = "wasmparser"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47b807c72e1bac69382b3a6fb3dbe8ea4c0ed87ff5629b8685ae6b9a611028fe"
+dependencies = [
+ "bitflags",
+ "hashbrown 0.15.5",
+ "indexmap",
+ "semver",
+]
+
 [[package]]
 name = "web-sys"
 version = "0.3.85"
@@ -3734,6 +3819,88 @@ name = "wit-bindgen"
 version = "0.51.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d7249219f66ced02969388cf2bb044a09756a083d0fab1e566056b04d9fbcaa5"
+dependencies = [
+ "wit-bindgen-rust-macro",
+]
+
+[[package]]
+name = "wit-bindgen-core"
+version = "0.51.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea61de684c3ea68cb082b7a88508a8b27fcc8b797d738bfc99a82facf1d752dc"
+dependencies = [
+ "anyhow",
+ "heck",
+ "wit-parser",
+]
+
+[[package]]
+name = "wit-bindgen-rust"
+version = "0.51.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b7c566e0f4b284dd6561c786d9cb0142da491f46a9fbed79ea69cdad5db17f21"
+dependencies = [
+ "anyhow",
+ "heck",
+ "indexmap",
+ "prettyplease",
+ "syn",
+ "wasm-metadata",
+ "wit-bindgen-core",
+ "wit-component",
+]
+
+[[package]]
+name = "wit-bindgen-rust-macro"
+version = "0.51.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0c0f9bfd77e6a48eccf51359e3ae77140a7f50b1e2ebfe62422d8afdaffab17a"
+dependencies = [
+ "anyhow",
+ "prettyplease",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wit-bindgen-core",
+ "wit-bindgen-rust",
+]
+
+[[package]]
+name = "wit-component"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9d66ea20e9553b30172b5e831994e35fbde2d165325bec84fc43dbf6f4eb9cb2"
+dependencies = [
+ "anyhow",
+ "bitflags",
+ "indexmap",
+ "log",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "wasm-encoder",
+ "wasm-metadata",
+ "wasmparser",
+ "wit-parser",
+]
+
+[[package]]
+name = "wit-parser"
+version = "0.244.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ecc8ac4bc1dc3381b7f59c34f00b67e18f910c2c0f50015669dde7def656a736"
+dependencies = [
+ "anyhow",
+ "id-arena",
+ "indexmap",
+ "log",
+ "semver",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "unicode-xid",
+ "wasmparser",
+]
 
 [[package]]
 name = "writeable"
@@ -3766,18 +3933,18 @@ dependencies = [
 
 [[package]]
 name = "zerocopy"
-version = "0.8.37"
+version = "0.8.39"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7456cf00f0685ad319c5b1693f291a650eaf345e941d082fc4e03df8a03996ac"
+checksum = "db6d35d663eadb6c932438e763b262fe1a70987f9ae936e60158176d710cae4a"
 dependencies = [
  "zerocopy-derive",
 ]
 
 [[package]]
 name = "zerocopy-derive"
-version = "0.8.37"
+version = "0.8.39"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1328722bbf2115db7e19d69ebcc15e795719e2d66b60827c6a69a117365e37a0"
+checksum = "4122cd3169e94605190e77839c9a40d40ed048d305bfdc146e7df40ab0f3e517"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -3846,9 +4013,9 @@ dependencies = [
 
 [[package]]
 name = "zmij"
-version = "1.0.19"
+version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3ff05f8caa9038894637571ae6b9e29466c1f4f829d26c9b28f869a29cbe3445"
+checksum = "b8848ee67ecc8aedbaf3e4122217aff892639231befc6a1b58d29fff4c2cabaa"
 
 [[package]]
 name = "zune-core"
diff --git a/Cargo.toml b/Cargo.toml
index f058bebf..768ddf46 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,30 +12,30 @@ tokio = { version = "1.49.0", features = ["rt-multi-thread", "macros", "io-util"
 tokio-util = { version = "0.7.18", features = ["io", "codec", "compat"] }
 tokio-stream = { version = "0.1.18", features = ["fs"] }
 bytes = "1.11.1"
-tempfile = "3.25.0"
+tempfile = "3.26.0"
 tower = "0.5.3"
 tower-http = { version = "0.6.8", features = ["fs", "compression-gzip", "compression-br", "trace", "cors", "add-extension", "request-id", "set-header", "limit"] }
 flate2 = "1.1.9"
 tracing = "0.1.44"
 tracing-subscriber = { version = "0.3.22", features = ["env-filter"] }
-chrono = { version = "0.4.43", features = ["serde"] }
+chrono = { version = "0.4.44", features = ["serde"] }
 http-body = "1.0.1"
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.149"
-futures = "0.3.31"
+futures = "0.3.32"
 async-stream = "0.3.6"
 mime_guess = "2.0.5"
-uuid = { version = "1.20.0", features = ["v4", "serde"] }
+uuid = { version = "1.21.0", features = ["v4", "serde"] }
 async-trait = "0.1.89"
 thiserror = "2.0.18"
 mockall = { version = "0.14.0", optional = true }
 sqlx = { version = "0.8.6", features = ["postgres", "runtime-tokio", "tls-rustls", "chrono", "uuid", "json"] }
-anyhow = "1.0.101"
-jsonwebtoken = { version = "10.1.0", features = ["rust_crypto"] }
+anyhow = "1.0.102"
+jsonwebtoken = { version = "10.3.0", features = ["rust_crypto"] }
 argon2 = "0.5.3"
 rand_core = { version = "0.6", features = ["std", "getrandom"] }
 hyper = { version = "1.8.1", features = ["full"] }
-quick-xml = "0.39.0"
+quick-xml = "0.39.2"
 dotenvy = "0.15.7"
 moka = { version = "0.12", features = ["future", "sync"] }
 http-range-header = "0.4"
@@ -49,7 +49,7 @@ percent-encoding = "2.3"
 reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls-webpki-roots"] }
 base64 = "0.22.1"
 fs2 = "0.4"
-rayon = "1.10"
+rayon = "1.11"
 infer = "0.19"
 async-compression = { version = "0.4", features = ["tokio", "gzip"] }
 async_zip = { version = "0.0.18", features = ["tokio", "deflate"] }
diff --git a/src/interfaces/api/handlers/caldav_handler.rs b/src/interfaces/api/handlers/caldav_handler.rs
index 852173ab..cf55caa9 100644
--- a/src/interfaces/api/handlers/caldav_handler.rs
+++ b/src/interfaces/api/handlers/caldav_handler.rs
@@ -23,6 +23,7 @@ use axum::{
 };
 use bytes::Buf;
 use percent_encoding::percent_decode_str;
+use std::fmt::Write;
 use std::sync::Arc;
 
 use crate::application::adapters::caldav_adapter::{CalDavAdapter, CalDavReportType};
@@ -694,26 +695,32 @@ fn generate_full_calendar_ical(
     calendar_name: &str,
     events: &[crate::application::dtos::calendar_dto::CalendarEventDto],
 ) -> String {
-    let mut ical = format!(
+    // Pre-estimate: ~200 bytes header + ~320 bytes per event
+    let mut buf = String::with_capacity(256 + events.len() * 320);
+    let _ = write!(
+        buf,
         "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//OxiCloud//NONSGML Calendar//EN\r\nX-WR-CALNAME:{}\r\n",
         calendar_name
     );
     for event in events {
-        ical.push_str(&generate_vevent(event));
+        write_vevent(&mut buf, event);
     }
-    ical.push_str("END:VCALENDAR\r\n");
-    ical
+    buf.push_str("END:VCALENDAR\r\n");
+    buf
 }
 
 fn generate_event_ical(event: &crate::application::dtos::calendar_dto::CalendarEventDto) -> String {
-    format!(
-        "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//OxiCloud//NONSGML Calendar//EN\r\n{}END:VCALENDAR\r\n",
-        generate_vevent(event)
-    )
+    let mut buf = String::with_capacity(512);
+    buf.push_str("BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//OxiCloud//NONSGML Calendar//EN\r\n");
+    write_vevent(&mut buf, event);
+    buf.push_str("END:VCALENDAR\r\n");
+    buf
 }
 
-fn generate_vevent(event: &crate::application::dtos::calendar_dto::CalendarEventDto) -> String {
-    let mut vevent = format!(
+/// Writes a VEVENT block directly into `buf` — zero intermediate allocations.
+fn write_vevent(buf: &mut String, event: &crate::application::dtos::calendar_dto::CalendarEventDto) {
+    let _ = write!(
+        buf,
         "BEGIN:VEVENT\r\nUID:{}\r\nSUMMARY:{}\r\nDTSTART:{}\r\nDTEND:{}\r\n",
         event.ical_uid,
         event.summary.replace('\n', "\\n"),
@@ -721,21 +728,21 @@ fn generate_vevent(event: &crate::application::dtos::calendar_dto::CalendarEvent
         event.end_time.format("%Y%m%dT%H%M%SZ"),
     );
     if let Some(ref desc) = event.description {
-        vevent.push_str(&format!("DESCRIPTION:{}\r\n", desc.replace('\n', "\\n")));
+        let _ = write!(buf, "DESCRIPTION:{}\r\n", desc.replace('\n', "\\n"));
     }
     if let Some(ref loc) = event.location {
-        vevent.push_str(&format!("LOCATION:{}\r\n", loc));
+        let _ = write!(buf, "LOCATION:{}\r\n", loc);
     }
     if let Some(ref rrule) = event.rrule {
-        vevent.push_str(&format!("RRULE:{}\r\n", rrule));
+        let _ = write!(buf, "RRULE:{}\r\n", rrule);
     }
-    vevent.push_str(&format!(
+    let _ = write!(
+        buf,
         "DTSTAMP:{}\r\nCREATED:{}\r\nLAST-MODIFIED:{}\r\nEND:VEVENT\r\n",
         event.updated_at.format("%Y%m%dT%H%M%SZ"),
         event.created_at.format("%Y%m%dT%H%M%SZ"),
         event.updated_at.format("%Y%m%dT%H%M%SZ"),
-    ));
-    vevent
+    );
 }
 
 // ─── DELETE ──────────────────────────────────────────────────────────