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perf(cachekit): an encrypted L1 hit on Node.js awaits no promise around the synchronous decrypt (LAB-12918) - #318
On Node.js an encrypted L1 hit from get(), exists() or wrap() now hands back a promise that has already settled. The NAPI decrypt is synchronous, yet the hit awaited four promises around it. In bench:ir, the new secure-get-l1-hit drops from 51,909 to 48,875 instructions per op (−5.84%) and secure-wrap-l1-hit-100b from 60,159 to 56,925 (−5.38%). Every A/A spread is 0.00%.
Closes LAB-12918
Change
EncryptionManagerCore.decryptNow() (package-internal). Once the keys are derived, a binding that returns a plain value decrypts in the call: it returns the plaintext, or throws the same EncryptionError that decrypt() rejects with. Before the keys are derived, after dispose(), and on Workers (WebCrypto decrypts asynchronously) it returns a Promise, so those paths behave as before. The public decrypt() is unchanged.
decodeEntry and decodeL1Entry return a value or a Promise.decodeEntry refuses oversized ciphertext and decrypts as before, then runs the unpack and decode in the same call when the decrypt did not suspend. decodeL1Entry keeps perf(cachekit): skip the decode's depth walks on an encrypted L1 hit this cache checked (LAB-12111) #290's behaviour on both branches: the first hit copies the bytes, walks the copy and swaps it into L1 if L1 still holds the original; later hits on the copy skip the walks; a failure drops the entry, is counted and logged, and rethrows when reliability.degradation is off.
The four hit sites await only a thenable:getEntry (behind get()), exists(), and both wrap() L1 reads (the SWR read, and the plain read a Worker takes with no waitUntil bound). This is the pattern from perf(cachekit): return a plaintext L1 hit without awaiting a decode (LAB-12110) #287. Each site decodes, and checks for a thenable, only when the cache encrypts, so the plaintext hit is unchanged.
A thenable check, not instanceof Promise. An async function returns the engine's own Promise, which fails instanceof once a library such as zone.js or Bluebird has replaced the global Promise. A cache's first decrypt, before its keys are derived, goes through such a function, and a Promise taken for a value is never awaited. src/utils/thenable.ts holds the one isThenable, shared with the manager.
Unchanged: the AAD, the keys and every stored byte; the ciphertext size cap; hit and miss counting; the SWR refresh decision. With degradation off, an L1 decrypt failure now throws inside the async hit path instead of rejecting a promise it awaits; callers still see a rejected promise.
decrypt() keeps its own copy of the binding call instead of sharing one with decryptNow(). A first version routed decrypt() through a shared helper. That changed how V8 inlined the napi-encrypted workload, which awaits decrypt() and encrypt(), and cost it 5.6% more instructions.
Sibling paths
path
this PR
get() encrypted L1 hit
changed
exists() encrypted L1 hit
changed
wrap() encrypted L1 hit, SWR read
changed
wrap() encrypted L1 hit, plain read (no waitUntil)
changed
encrypted L2 read
decrypt no longer awaits key init: secure-set-get −0.35%
set() encrypt
not changed: it awaits encrypt(), which awaits key init, then awaits the backend write
Workers
not applicable: WebCrypto decrypts asynchronously, so the hit still awaits it
cachekit-py, cachekit-rs
no equivalent cost: a coroutine or future that returns without suspending does not yield
Tests
cache.encryption-l1.test.ts, "an encrypted L1 hit awaits only a decrypt that suspends": on Node.js, each get(), exists() and wrap() hit (SWR read and plain read), first hit and later hits, settles in as many microtask turns as Promise.resolve(). With bindings that return Promises, as Workers' do, the same hits take more turns, serve the right value and still swap the first hit's copy into L1. A substituted ciphertext is dropped and logged under both degradation settings, with a synchronous and with a suspending decrypt. With the global Promise replaced by a subclass, a fresh cache's get() from L1 and L2 and both wrap() reads decode the value, and exists() drops a substituted entry.
manager-core.test.ts covers decryptNow(): a Promise before key derivation, a plain value after it, the EncryptionError it throws, rejection after dispose(), and the binding's Promise with its rejection mapped.
encryption.protocol.test.ts: the aad_hex vectors now also check the AAD decryptNow() hands the binding.
cache.l1-trusted.test.ts: the race between a first hit and a rewrite of its key now needs a decrypt that suspends, because on Node.js the hit no longer yields. The test makes one suspend.
Tests that counted or failed the cache's decrypts now intercept decryptNow, which the cache calls. The settle-turn helper moved to test/fixtures/settle.ts, shared with the plaintext tests from perf(cachekit): return a plaintext L1 hit without awaiting a decode (LAB-12110) #287, and now fails after 1,000 turns instead of spinning on a read that waits on a timer or I/O.
Mutants: at each of the four hit sites, putting the await back unconditionally fails a settle test, and checking instanceof Promise instead of a thenable fails a replaced-Promise test; the same holds for decodeEntry and decodeL1Entry. Making decryptNow() always go through decrypt() fails three tests; dropping the failure handler or the copy swap on the Promise branch fails the suspending tests.
Local runs: on Node.js 24.22.1, vitest run passed 2,868 tests (1 skipped), test:protocol 1,004 and test:workers 307. The full suite also passed on Node.js 22.23.4. eslint, type-check, type-check:tests, prettier on the changed files and check:workers-bundle are clean.
Benchmarks
bench:ir gains secure-get-l1-hit: cache.get() served from an encrypted L1, 100 B of msgpack, with no key generation. Both builds ran 8 workloads with 3 repeats and the same workload file, on the same machine (Node.js 24.22.1, valgrind 3.22.0).
workload
main
this branch
delta
A/A (branch)
secure-get-l1-hit (new)
51,909
48,875
−5.84%
0.00%
secure-wrap-l1-hit-100b
60,159
56,925
−5.38%
0.00%
secure-wrap-l1-hit-10kb
1,522,412
1,519,659
−0.18%
0.00%
secure-set-get (L1 off)
492,594
490,856
−0.35%
0.00%
napi-encrypted
41,499
41,504
+0.01%
0.00%
get-l1-hit
2,113
2,114
+0.05%
0.00%
wrap-l1-hit
17,159
17,157
−0.01%
0.00%
wrap-l1-hit-int
2,359
2,364
+0.21%
0.00%
The A/A spread on main is 0.00% for all eight. The hit saves about 2,800 to 3,200 instructions whatever the value's size, so the share falls as the decode grows: −0.18% at 10 KB. wrap-l1-hit-int is served from the key memo's held entry before any changed code runs; its +5 instructions are code layout. secure-get-l1-hit has no ir-seconds.json row yet, so the shard split counts it as the median row, 31 s; add its row from this gate's base.json.
On Node.js the NAPI decrypt is synchronous, yet an encrypted L1 hit
awaited four promises around it: the decode, the L1 decode, decrypt()
and its ensureInitialized(). Once the keys are derived the manager's new
decryptNow() decrypts in the call, decodeEntry and decodeL1Entry return
a value or a Promise, and the get(), exists() and wrap() hit sites await
only a Promise. Workers, where WebCrypto decrypts asynchronously, and a
manager not yet initialised keep the await. The first-hit copy and
trust, drop-on-failure and the degradation policy are unchanged.
Adds the secure-get-l1-hit bench workload.
… hit
decryptNow() takes the binding call into its own body instead of
sharing one with decrypt(): routing decrypt() through it changed how V8
inlined a caller awaiting decrypt() and encrypt(), +5.6% instructions on
napi-encrypted. States in the README that an encrypted L1 hit on Node.js
awaits no promise, lists secure-get-l1-hit in CONTRIBUTING and gives it
an ir-seconds row.
No actionable comments were generated in the recent review.
Summary by CodeRabbit
Performance
Encrypted cache reads in Node.js can complete synchronously after keys are ready, avoiding unnecessary asynchronous waits. This applies to get(), exists() and wrap(); Cloudflare Workers continue to use asynchronous decryption.
Documentation
Updated performance guidance to explain the difference between Node.js and Workers for encrypted cache operations.
Benchmarks
Added a benchmark for repeated encrypted L1 cache hits, measuring reads served from the in-memory cache.
Walkthrough
The change adds decryptNow() for synchronous or asynchronous decryption. Encrypted L1 reads now await only when decryption returns a thenable. Tests cover both decryption paths, and the benchmark and performance documentation describe encrypted L1 hits.
Changes
Encrypted L1 reads
Layer / File(s)
Summary
Add synchronous decryption support packages/cachekit/src/utils/thenable.ts, packages/cachekit/src/encryption/manager-core.ts, packages/cachekit/src/encryption/manager-core.test.ts, packages/cachekit/test/protocol/encryption.protocol.test.ts, packages/cachekit/src/encryption/manager.ts
EncryptionLike and EncryptionManagerCore now expose decryptNow(), which returns plaintext directly for synchronous bindings or a promise for asynchronous results. Tests cover return values, error mapping and AAD. The usage example awaits encrypt() and decrypt().
Cache decoding and the get(), exists() and wrap() L1 paths now handle direct and promise results. Tests cover both paths, failure handling, L1 trust and promise-settling behaviour.
Measure and describe encrypted L1 hits packages/cachekit/bench/ir-workload.mjs, CONTRIBUTING.md, packages/cachekit/README.md
The secure-get-l1-hit benchmark measures encrypted L1 reads. The documentation distinguishes synchronous Node.js decryption from asynchronous Cloudflare Workers decryption.
sequenceDiagram
participant CacheCore
participant EncryptionManagerCore
participant EncryptionBinding
CacheCore->>EncryptionManagerCore: decryptNow(ciphertext, cacheKey)
EncryptionManagerCore->>EncryptionBinding: decrypt with tenant keys
alt Binding returns plaintext
EncryptionBinding-->>EncryptionManagerCore: plaintext bytes
EncryptionManagerCore-->>CacheCore: plaintext bytes
CacheCore-->>CacheCore: decode L1 result without awaiting
else Binding returns a promise
EncryptionBinding-->>EncryptionManagerCore: promise of plaintext bytes
EncryptionManagerCore-->>CacheCore: promise of plaintext bytes
CacheCore-->>CacheCore: await decryption and decode L1 result
end
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Possibly related PRs
cachekit-io/cachekit-ts#271: Updates encryption binding return types and adds asynchronous Workers WebCrypto bindings used by decryptNow().
Merge Risk: Minimal · up to 0409a
The previously reported test-hang risk has been addressed. No actionable issue remains before merge, subject to normal checks.
Pre-merge checks: 5
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Title check
The title names the change: an encrypted L1 hit on Node.js no longer awaits a promise around the synchronous decrypt. The changeset adds decryptNow(), makes the get/exists/wrap L1 hit paths await only…
Description check
The description explains the problem and the change. It covers the decryptNow() addition, the decodeEntry and decodeL1Entry changes, the thenable check, the sibling paths, tests, mutation checks and b…
Docstring Coverage
Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
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The title names the change: an encrypted L1 hit on Node.js no longer awaits a promise around the synchronous decrypt. The changeset adds decryptNow(), makes the get/exists/wrap L1 hit paths await only thenables, and adds isThenable and the settle fixture. The scope prefix and ticket reference are acceptable. The title is specific and matches the main change.
Full details: Description check
Explanation
The description explains the problem and the change. It covers the decryptNow() addition, the decodeEntry and decodeL1Entry changes, the thenable check, the sibling paths, tests, mutation checks and benchmark results. It matches the changeset in detail.
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Reviewing files that changed from the base of the PR and between d3d4e04 and 0409a5c.
Files selected for processing: 3
packages/cachekit/src/cache.encryption-l1.test.ts
packages/cachekit/src/utils/thenable.ts
packages/cachekit/test/fixtures/settle.ts
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A code review identified the following issues in this pull request.
Each section describes what was found and includes a reference implementation where available.
Files involved:
- packages/cachekit/src/cache.encryption-l1.test.ts:420
---
### [1/1] packages/cachekit/src/cache.encryption-l1.test.ts:420
Issue identified during code review:
Unsafe type assertion in packages/cachekit/src/cache.encryption-l1.test.ts (also at line 422): `keys as TenantKeys` passes `keys` to `encryptWithTenantKeys(plaintext, aad, keys)` with no compile-time or runtime check that it matches `TenantKeys`. If `keys` is missing a field that `TenantKeys` requires, the type checker accepts the call, and `encryptWithTenantKeys` fails at runtime with a misleading test error. Fix: declare `keys` with type `TenantKeys` (or narrow it with a type guard) and drop the `as TenantKeys` cast.
---
Review each issue in context, use the reference implementations as guidance, and apply fixes that are consistent with the surrounding codebase.
…is replaced
The value-or-Promise checks used instanceof Promise. An async function
returns the engine's own Promise, which fails instanceof once a library
such as zone.js or Bluebird has replaced the global, so a cache's first
decrypt, before its keys are derived, was taken for a value: an L1 hit
served undefined and an L2 read failed to decode. The checks now test
for a thenable, through one isThenable shared with the manager.
Also pins decryptNow()'s AAD against the protocol vectors, names the
trust and failure helpers for what they do, shares the settle-turn test
helper, and drops the estimated ir-seconds row: a workload with no row
counts as the median.
Head 0409a5c against base f9c93d01cc0df9e8d551510eb1d84032cb96973b, Node v24.22.2, valgrind-3.26.0. Instructions per op on the main thread (bench:ir --compare); median of the repeats, A/A = (max − min) / median. A workload fails above +2.00% and warns above +1.00% (its own threshold: plaintext-set-1mb at +10.00%, napi-encrypted at +4.00%, warning at half); an A/A over 0.40% reads INCONCLUSIVE.
The thenable check ran on the plaintext branch of the get() and wrap()
hit sites too, +9 instructions on get-l1-hit. Each site now decodes and
checks only when the cache encrypts, as exists() already did.
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Actionable comments posted: 1
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Inline comments:
Review comments at @packages/cachekit/test/fixtures/settle.ts:
- Around line 12-15: Bound the microtask polling loop in the settle fixture by
limiting the turns counter and failing when that limit is exceeded. Preserve the
existing behaviour for reads that settle within the limit; do not let continued
polling starve the event loop.
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On Node.js an encrypted L1 hit from
get(),exists()orwrap()now hands back a promise that has already settled. The NAPI decrypt is synchronous, yet the hit awaited four promises around it. Inbench:ir, the newsecure-get-l1-hitdrops from 51,909 to 48,875 instructions per op (−5.84%) andsecure-wrap-l1-hit-100bfrom 60,159 to 56,925 (−5.38%). Every A/A spread is 0.00%.Closes LAB-12918
Change
EncryptionManagerCore.decryptNow()(package-internal). Once the keys are derived, a binding that returns a plain value decrypts in the call: it returns the plaintext, or throws the sameEncryptionErrorthatdecrypt()rejects with. Before the keys are derived, afterdispose(), and on Workers (WebCrypto decrypts asynchronously) it returns a Promise, so those paths behave as before. The publicdecrypt()is unchanged.decodeEntryanddecodeL1Entryreturn a value or a Promise.decodeEntryrefuses oversized ciphertext and decrypts as before, then runs the unpack and decode in the same call when the decrypt did not suspend.decodeL1Entrykeeps perf(cachekit): skip the decode's depth walks on an encrypted L1 hit this cache checked (LAB-12111) #290's behaviour on both branches: the first hit copies the bytes, walks the copy and swaps it into L1 if L1 still holds the original; later hits on the copy skip the walks; a failure drops the entry, is counted and logged, and rethrows whenreliability.degradationis off.getEntry(behindget()),exists(), and bothwrap()L1 reads (the SWR read, and the plain read a Worker takes with nowaitUntilbound). This is the pattern from perf(cachekit): return a plaintext L1 hit without awaiting a decode (LAB-12110) #287. Each site decodes, and checks for a thenable, only when the cache encrypts, so the plaintext hit is unchanged.instanceof Promise. An async function returns the engine's own Promise, which failsinstanceofonce a library such as zone.js or Bluebird has replaced the globalPromise. A cache's first decrypt, before its keys are derived, goes through such a function, and a Promise taken for a value is never awaited.src/utils/thenable.tsholds the oneisThenable, shared with the manager.Unchanged: the AAD, the keys and every stored byte; the ciphertext size cap; hit and miss counting; the SWR refresh decision. With degradation off, an L1 decrypt failure now throws inside the async hit path instead of rejecting a promise it awaits; callers still see a rejected promise.
decrypt()keeps its own copy of the binding call instead of sharing one withdecryptNow(). A first version routeddecrypt()through a shared helper. That changed how V8 inlined thenapi-encryptedworkload, which awaitsdecrypt()andencrypt(), and cost it 5.6% more instructions.Sibling paths
get()encrypted L1 hitexists()encrypted L1 hitwrap()encrypted L1 hit, SWR readwrap()encrypted L1 hit, plain read (nowaitUntil)decryptno longer awaits key init:secure-set-get−0.35%set()encryptencrypt(), which awaits key init, then awaits the backend writeTests
cache.encryption-l1.test.ts, "an encrypted L1 hit awaits only a decrypt that suspends": on Node.js, eachget(),exists()andwrap()hit (SWR read and plain read), first hit and later hits, settles in as many microtask turns asPromise.resolve(). With bindings that return Promises, as Workers' do, the same hits take more turns, serve the right value and still swap the first hit's copy into L1. A substituted ciphertext is dropped and logged under both degradation settings, with a synchronous and with a suspending decrypt. With the globalPromisereplaced by a subclass, a fresh cache'sget()from L1 and L2 and bothwrap()reads decode the value, andexists()drops a substituted entry.manager-core.test.tscoversdecryptNow(): a Promise before key derivation, a plain value after it, theEncryptionErrorit throws, rejection afterdispose(), and the binding's Promise with its rejection mapped.encryption.protocol.test.ts: theaad_hexvectors now also check the AADdecryptNow()hands the binding.cache.l1-trusted.test.ts: the race between a first hit and a rewrite of its key now needs a decrypt that suspends, because on Node.js the hit no longer yields. The test makes one suspend.decryptNow, which the cache calls. The settle-turn helper moved totest/fixtures/settle.ts, shared with the plaintext tests from perf(cachekit): return a plaintext L1 hit without awaiting a decode (LAB-12110) #287, and now fails after 1,000 turns instead of spinning on a read that waits on a timer or I/O.Mutants: at each of the four hit sites, putting the await back unconditionally fails a settle test, and checking
instanceof Promiseinstead of a thenable fails a replaced-Promisetest; the same holds fordecodeEntryanddecodeL1Entry. MakingdecryptNow()always go throughdecrypt()fails three tests; dropping the failure handler or the copy swap on the Promise branch fails the suspending tests.Local runs: on Node.js 24.22.1,
vitest runpassed 2,868 tests (1 skipped),test:protocol1,004 andtest:workers307. The full suite also passed on Node.js 22.23.4. eslint,type-check,type-check:tests, prettier on the changed files andcheck:workers-bundleare clean.Benchmarks
bench:irgainssecure-get-l1-hit:cache.get()served from an encrypted L1, 100 B of msgpack, with no key generation. Both builds ran 8 workloads with 3 repeats and the same workload file, on the same machine (Node.js 24.22.1, valgrind 3.22.0).mainsecure-get-l1-hit(new)secure-wrap-l1-hit-100bsecure-wrap-l1-hit-10kbsecure-set-get(L1 off)napi-encryptedget-l1-hitwrap-l1-hitwrap-l1-hit-intThe A/A spread on
mainis 0.00% for all eight. The hit saves about 2,800 to 3,200 instructions whatever the value's size, so the share falls as the decode grows: −0.18% at 10 KB.wrap-l1-hit-intis served from the key memo's held entry before any changed code runs; its +5 instructions are code layout.secure-get-l1-hithas noir-seconds.jsonrow yet, so the shard split counts it as the median row, 31 s; add its row from this gate'sbase.json.