RFC 10008: The new HTTP Query Method

(rfc-editor.org)

211 points | by schappim 6 hours ago

25 comments

  • 100ms 5 hours ago
    Including a strong motivating example might have helped sell this, using an example that could trivially be expressed as a GET is extremely distracting.

    Even imagining a QUERY with a large JSON filtering structure, or say an image input as request body, it feels extremely odd to include the request body as part of the cache key. It also implies an unbounded and user-controlled cache key, with the only really meaningful general caching strategy being bitwise compare of the request body (or a hash), which in a hostile scenario implies cache busting would be trivial.

    This invokes multiple semantic oddities in one go with obvious difficulties for a very niche use case. If I'm writing a service that needs complex filtering or complex input like an image, any form of caching (e.g. individual data columns of a join, or embeddings keyed by perceptual hashes of a decoded image input) is going to be far away from the HTTP layer and certainly unrelated to the exact bit representation of the request on the wire.

    Why even bother trying to capture this in a generic way?

    I would be far more inclined to try and capture this caching semantic as a new header for POST. Something like "Vary: request-body" or similar. Perfectly backwards compatible and perfectly ignorable for all but the 0.1% of CDN use cases where the behaviour might turn out useful

    • Joker_vD 5 hours ago
      > It also implies an unbounded and user-controlled cache key,

      The query part of GET's URI is also barely bounded in practice and user-controlled, and is indeed used as part of the cache key (because it's a part of URI), so I am not sure why you raise this objection at all.

      • giancarlostoro 4 hours ago
        > and user-controlled

        I've found some sites that tack on a session ID and if you try to tamper with the URL in any way, it sends you back to "Page 1" really annoys me lol at that point let me skip to any page with your web UI.

      • PunchyHamster 3 hours ago
        Well, because it is more code. Current caching software caches by headers + query string. It now needs to be expaned to cache by body too.

        It feels very pointless and there is no drawback of just using POST

        • OvervCW 3 hours ago
          There is: your browser or other type of client does not know it can repeat a POST request if it fails, whereas a QUERY request can be freely repeated in case of errors.
        • afavour 3 hours ago
          Is caching not the primary reason to use this over POST? You should never want to cache POST requests.
    • CodesInChaos 4 hours ago
      The browser can simply store a collision resistant hash (e.g. SHA-256) of the body, if it wants a smaller cache key. I can't really think of any caching related attacks that don't equally apply to a query parameter. Generating a unique 30 character query parameter is just as easy as generating a 30 MB request body, if you want to flood the cache.
      • ralferoo 3 hours ago
        Not necessarily that simple, as you'd have sort all the input parameters to maintain a useable cache key. Not especially difficult, but if the data is large and so re-allocation and sorting is required, then you're starting to open up the attack surface where bugs might have been introduced.
    • tanepiper 2 hours ago
      One example - I'm building an MCP server at the moment for a database I'm working on. In ChatGPT I want to do dry-run posts first that roll back before committing - both are POST requests with a property - and it loves to trigger the safety layer in the tools (for various reasons, it's hard to debug exact causes)

      But I think this would make it better - QUERY before POST means different request types, not just the same with a safety flag.

    • cryptonym 5 hours ago
      Sure you can provide an image as request body, but you could already do it with b64 query parameter. If you try hard enough, you can poorly use any proposed standard. GET with query parameters already is opaque and makes cache busting trivial.
      • layer8 4 hours ago
        Query parameters are length-limited, because HTTP URIs are: https://www.rfc-editor.org/info/rfc9110/#section-4.1-5. There is no expectation for arbitrarily long HTTP URLs to be functioning.
        • cryptonym 4 hours ago
          Your link doesn't say URIs are length-limited
          • Draiken 4 hours ago
            I'm guessing you never hit this issue then, but it's a real issue. Whether or not it's in the RFC as a hard limit it doesn't matter, no HTTP server will allow unlimited sized URIs.

            You simply can't base64 large payloads and you're stuck with workarounds.

            • cryptonym 4 hours ago
              You are guessing wrong. Thanks, I know specific implementation will come with their limits. This will equally apply to QUERY body size and caching strategy.

              Are we seriously ok with linking the RFC as source while providing a statement that doesn't match? RFC does matter.

              • ralferoo 3 hours ago
                The RFC does say "It is RECOMMENDED that all senders and recipients support, at a minimum, URIs with lengths of 8000 octets in protocol elements."

                One can infer from the RFC that you can reasonably expect many implementations to fail beyond 8000 characters, and that there are no guarantees up to that either.

                True, the RFC doesn't specify a limit, but it does clearly indicate that it's not unbounded, nor should you expect it to be.

    • inigyou 3 hours ago
      Not all usage scenarios are the public internet, and something doesn't have to be useful on the public internet to be standardized.

      Realistically, systems for the public internet will use a secure hash as the cache key so it'll always be the same size. The cache key already includes a URL that can be very long, and an arbitrary set of header values.

      • ralferoo 3 hours ago
        Except that by definition, in a URL the data has no implicit meaning so for a cache hit you need an exact match, including order and case, but for a list of POST parameters, they could legitimately be in any order and so you can't just hash it all as a blob, you need to sort the keys, possibly copy data around (unless using keys plus hash), probably allocating more memory, etc. I'm pretty certain we'll see at least one CVE out of the first few implementations of this!
        • inigyou 2 hours ago
          POST/QUERY data can be in any format. Who are you to say order doesn't matter? Are you sure you can even parse it? Mine is in DES-encrypted (with key "password") base85 DER, you really gonna implement that in your proxy?
    • epolanski 5 hours ago
      > Why even bother trying to capture this in a generic way?

      I guess it's about resolving the odd semantics of using POST which is not idempotent and thus allowing easier control flow of caches and retrys.

      Your perspective is 100% correct if you think at the application-layer, but with a dedicated method, you can have that behaviour out-of-the-box out of your HTTP infrastructure (whether it's at your hyperscaler's router or your apache/nginx/browser whatever) and stop implementing yourself the post-as-a-query edge case.

    • friendzis 5 hours ago
      > It also implies an unbounded and user-controlled cache key.

      While the concern is valid, caching is entirely optional at query level, therefore it is totally valid to cache only certain "filters".

    • davidkwast 5 hours ago
      I would use a hash of the body content (the query) as a URL parameter

      /?hash=123456789

      • Joker_vD 5 hours ago
        Why? That's pushing more work to do both on yourself and the cache.
    • wang_li 4 hours ago
      If you control the full stack then the functionality described here can be implemented with POST. The only way this comes into play is if some second party client of your service is trying to impose rules on how your backend works. My answer to that is no. I will be defining the contract by which my services operate.
  • CodesInChaos 5 hours ago
    I wonder if HTML forms will add support for QUERY:

        <form action="..." method="query">
    
    This would avoid the annoying re-submission warnings you're getting if you refresh a page that was returned by a POST form submission, since QUERY is required to be idempotent.
    • acabal 57 minutes ago
      Supporting more than GET/POST in HTML forms has been my dream for decades. There's a WHATWG proposal to do just that if you want to add your voice: https://github.com/whatwg/html/pull/11347
    • chrismorgan 33 minutes ago
    • bob1029 4 hours ago
      This is better solved with the post redirect get pattern.
      • diroussel 52 minutes ago
        That is the good old fashion workaround. But why is it better than a form causing an HTTP QUERY.

        If we can do QUERY forms, it would be an ideal time to add JSON encoding for forms.

    • amluto 3 hours ago
      One oddity of forms: the result of a form POST is a page that has a location (the URL) but that cannot loaded via that location. As far as I know, the fact that the page is a POST and not a GET is not stored anywhere visible to the user or to JS. And refresh works oddly.

      If method=QUERY were added, there would be a new variety of this weirdness.

      • sheept 2 hours ago
        At least browsers wouldn't have to warn users that they'd be resubmitting data if they reload the page after submitting a query form, since query requests are intended to be idempotent
        • amluto 1 hour ago
          You still get the nastiness that the Sec-Fetch-* state gets mostly trashed when you hit refresh. And someone would need to figure out how CORS preflight interacts with refresh, which is not currently an issue with POST. (The current "simple request" behavior or whatever it's called is a real mess and is the cause of a lot of CSRF vulnerabilities.)
    • tempfile 4 hours ago
      Depends whether your form submission should expect side effects or not. Most forms submissions have side effects. If the effect is truly idempotent, wouldn't PUT be a better verb? That is also supposed to be idempotent.
      • echoangle 3 hours ago
        You can’t use PUT as a form action though.
      • diroussel 49 minutes ago
        GET and QUERY are both idempotent.
    • 100ms 5 hours ago
      Forms, HTTP implementations, public API surfaces, and all for what exactly. Introducing a new verb for this feels profoundly misplaced
      • jagged-chisel 4 hours ago
        Idempotency is an important attribute for correctness. Yep, you can document that POSTing to $ENDPOINT is idempotent, but you can't communicate that to caching layers throughout the network. QUERY, by definition, is idempotent and cacheable.
        • resters 1 hour ago
          Great point. I wish more people realized that intuitively.
        • jnewton_dev 4 hours ago
          Does anyone know if this approach works at significantly larger scales? Curious about where it breaks down.
          • inigyou 3 hours ago
            Larger scales like what? I expect that everywhere you currently cache GETs you can cache QUERYs. But does caching GETs work at scale?
      • alpinisme 4 hours ago
        At least support - or lack thereof - for a new verb is unambiguous (compared to changing the semantics of GET)
    • ctdinjeu7 5 hours ago
      Now HN’s UX can finally be decent.

      The team will have to wait for a new header and textarea specs to fix the rest of the jank.

      This site is so awful lol. Why don’t they update it?

      • CodesInChaos 4 hours ago
        Where does HN use POST for safe operations? I can't think of any.

        Comment submission isn't safe, so QUERY can't be used there. And it doesn't suffer from the problem anyways, since HN returns a 3XX on successful submission, so refreshing doesn't show a warning.

  • ynac 3 hours ago
    Just in case anyone wants to pretend it's still that other century:

    https://www.rfc-editor.org/rfc/rfc10008.txt

    • jjice 3 hours ago
      I'll forever love a long, totally plain text document like this. So many good times with video game FAQs as a kid. It really is a superior form of information in a lot of ways (not all).
      • riffic 3 hours ago
        I have a thesis brewing that explores how rich text WYSIWYG editors create a "what you see is all there is" cognitive bias, while plain text overcomes it.
    • riffic 3 hours ago
      beautiful formatting. I should crib this style template for internal work memos, it's timeless.
  • piterrro 4 hours ago
    > GET request with a body was heavily considered by the IETF working group, but it was ultimately rejected in favor of creating the new QUERY method. The decision to create a distinct method came down to historical interoperability issues and strict compliance with the core architectural definitions of HTTP.

    I've been sending request body along GET method for years now

    • huskyr 4 hours ago
      Apparently some load balancers drop the body.
      • inigyou 3 hours ago
        I expect all sorts of intermediaries may drop the body, since having a body is forbidden by the standard.

        When it's your client talking to your server you can obviously do whatever you want - it doesn't cause problems until you want to involve third-party code, such as a reverse proxy (such as nginx) or a CDN. This includes proxies your customers may be using.

    • preisschild 3 hours ago
      > I've been sending request body along GET method for years now

      Generally not a great idea. With some http implementations this is not even possible (for example, fetch)

      https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/U...

      > You cannot include a body with GET requests

      And transparent caching might result in weird issues.

  • barbazoo 1 hour ago
    > GET: Content (body) "no defined semantics"

    I thought it wouldn't be a terrible idea to open up the GET method to contain a body but according to the original spec the GET body is to be ignored completely. There's also caching which would break because the important bit of the request would live in the stripped body.

  • stymaar 1 hour ago
    Why not standardize a body in the GET request (which isn't forbidden per spec and works in many places already but isn't supported everywhere because it's not mandated to support it)?
    • mholt 18 minutes ago
      Too many servers ignore/drop/reject body in GET requests. RFC 9110 does allow it, but is only recommended if server documentation states that it is supported.
      • stymaar 8 minutes ago
        These servers will likely also reject the QUERY request though…
        • greghines 1 minute ago
          But at least in that case you may get a much more meaningful 405 Method Not Allowed response rather than the server just silently dropping the GET body content.
  • simon84 1 hour ago
    This whole thing is non sense. It basically mixes technical constraints (body or not body) with a functional requirement that arises from people that are tied to semantics of the protocol.

    HTTP is transfer protocol. It should not ever imply anything at the business level.

    Yes REST made it's worst mistake out if it by giving a meaning to the verb.

    Yes proxies rule how the body is re-interpreted in spite of the will of the sender (wtf).

    But the original RFC states clearly that any verb can be used. This is how WebDav normalised its own.

    But playing fancy by introducing a change that all HTTP implementation will have to honor is a very bad and irrational choice.

  • andltsemi3 5 hours ago
    If this is actually going to replace GET requests w/ query strings in the wild, Im very much hoping for browser bookmarks to support keeping request parameters.
    • inigyou 5 hours ago
      Probably won't. Probably will replace whenever POST is currently used for a query.
  • pwdisswordfishq 5 hours ago
    Wait, it's already past 10 thousand?
    • rhplus 5 hours ago
      Someone has an ambiguous bet predicting when RFC 10000 will be published, but the numbers went straight from 9998 to 10008. No-one wins!

      https://manifold.markets/CollectedOverSpread/when-will-rfc-1...

      • ekr____ 4 hours ago
        RFC 10000 will not be published. They're just going to skip past the number.

        https://mailarchive.ietf.org/arch/msg/tools-discuss/EpoQcVt_...

        RFC #s are issued sometime before publication, so they can come out out of order. I would expect 9999, 10001, etc. to show up eventually.

      • echoangle 3 hours ago
        > This question resolves to the month of publication of the lowest-numbered RFC with a number greater than or equal to 10000.

        So of 10008 is the first one after 10000, that date is the one to bet on.

      • Imustaskforhelp 5 hours ago
        Everytime I think that prediction markets bets can't get worse, they do, all in weird ways. I never expected someone betting over when RFC 10,000 will be published but somehow its fits just about right for prediction markets.

        just wow, people seem to be having too much money it seems for them to bet over when RFC's are gonna get released.

        This isn't even one of the worst offenders on prediction market or even comparable to it but I am just amazed (in a negative manner, surprised? its just strange) by the depth on what people actually bet on these markets.

        • networked 5 hours ago
          People aren't betting real money on this. Manifold uses "mana" points similar to HN karma, which is why you get more for-fun silly bets. I don't see anything inherently wrong with it. Disclosure: my mana net worth is 75k; I haven't been active on Manifold.
          • Imustaskforhelp 4 hours ago
            Ah okay. I didn't know that.

            Interesting thing actually. Seems similar to the trend in South Korea recently where you can online shop to get the thrill of shopping but you aren't actually paying with money.

            But I am unsure of the overlap between manifold and polymarket/kalshi. I imagine that some might win in manifold and try to bet on polymarket to win "real" money which ends up being a bit gambling-esque.

            But good for manifold for atleast not playing with real money but rather points like this. I would argue that Manifold might be better than polygon/kalshi in terms of net positive outcome of its existence for the world perhaps.

            • networked 4 hours ago
              Interesting trend. I have found a short article about it: https://www.odditycentral.com/news/south-koreas-fake-online-.... It seems nothing long-form has been written about it in English yet.

              There is an overlap between Manifold and Polymarket/Kalshi. At the very least, Polymarket is more liquid, which creates opportunities for arbitrage and incentives for Manifold users to follow Polymarket. There is something at stake on Manifold itself if you choose to pursue it. There have been ways to convert mana to charitable donations (to your preferred charity), tickets to Manifest (the Manifold conference), and also merch and now prize drawings. Mana is like HN karma in that being at the top gives you status and bragging rights and suggests technical competence.

  • tonympls 3 hours ago
    As "just a guy that programs" (ok, now guides agents to program) and tries to follow the rules (with a big dose of pragmatism), this totally makes sense to me. This is also the first time I've seen or heard about this coming.

    I like that we now have a way to not being forced to define Resources when we want to query. It always felt like I was missing something that there could be an infinite, defined-on-the-fly number of Resources for a "part" of a given Resource. Do I really want to define "all cats that sleep more than 20 hours a day and like sunbeams and want to eat breakfast at 3 am" as a Resource? (ok, we all know that is actually the full set of cats). I'm ok that you want to define that as a Resource but in my system, it makes more sense that Cats is the Resource and I just need some accepted way to query.

    I like the implementation (again, as just a guy that programs). I don't see how it could have done it better or simpler which probably hides the complexity of getting there.

    I also especially appreciate how the spec is written. Opening a spec, I wonder how far I'll get before I don't know what the heck they're talking about (and, again, as just a guy that programs). I don't think it's easy to write a spec that is complete and approachable like this. Really appreciate that.

    • inigyou 3 hours ago
      The standards have always been a bit more abstract than you use in practice. Common practice prior to this would be /catsearch?sleep=20&sunbeams=yes&breakfast=0300 where the "resource" is /catsearch and the rest are query parameters, but you could also use /catsearch/sleep/20/sunbeams/yes/breakfast/0300 which looks like a "resource", but nobody is actually enforcing that it is a "resource".
  • drob518 30 minutes ago
    Aside: Wow, we’ve hit 5-digit RFC numbers now!
  • smashed 4 hours ago
    Use the QUERY method in your http query to query search results. Do not add query parameters.

    I think the name is confusing because the term 'query' is already used to refer to http requests in general.

    Just the title of the RFC confused me.

    • comfydragon 2 hours ago
      > the term 'query' is already used to refer to http requests in general

      In what circles is this the case? I sometimes colloquially refer to a GET request as a query, but definitely not so on a POST, PUT or DELETE.

  • toybeaver 5 hours ago
    This makes me happy tbh, I was never a fan of creating `POST /search` endpoints when working with robust APIs
  • mlhpdx 3 hours ago
    Wow, it still isn’t a standard? I’ve been building with the QUERY method for years now.

    I’ve enjoyed the combination with Range headers for paging, despite this tidbit:

    > It is expected that these built-in features will be used instead of HTTP Range Requests

    Using the QUERY request as the definition of a set, and Range to retrieve subsets seems very natural.

  • etchalon 21 minutes ago
    Why does this feel like GraphQL demanding everyone else solve their problems?
  • CodeWriter23 48 minutes ago
    It's about time.
  • cosmotic 2 hours ago
    Why not just define the semantics of a GET request body?
    • advisedwang 1 hour ago
      There's countless proxies in the wild that would not behave correctly with an RFC-defined GET-with-body, and there's no way for a client to know if that's the case.

      QUERY has the advantage of getting default behaviour from most proxies (which at least is well behaved even if inefficient). If there are any proxies that just drop QUERY requests, at least they won't silently mangle the request.

      This is the same way that instead of improving how HTTP 301 was specified, HTTP 308 was created. It's a pragmatic move.

    • chadgpt3 2 hours ago
      Proxies often delete it
      • elAhmo 2 hours ago
        They could be updated to not delete it, like they would require for this new method anyway.
        • moralestapia 2 hours ago
          Agree.

          They should not delete the body in the first place.

          • jerf 3 minutes ago
            If we're going to play the "should" game, whatever originated the body "shouldn't" have because the spec says that's illegal.

            Although we could also go with, a proxy shouldn't delete the body, it "should" reject the request outright as ill-formed.

            The meta-point I'm making here, which I'm sure will be missed if I don't spell it out, is that if we're going to talk about what "should" be done when it is explicily out of the scope of a standard, there's no way around the fact that there are multiple completely sensible ways to extend the standard and there's every reason to expect that in the real world people aren't going to agree. Sometimes they manage to, but even then often quite imperfectly. Our human intuitions that standards are something that are "built" is perhaps not wrong, but you can also productively look at standards as taking the raw material of all possible things two systems could send to each other and removing possibilities. If you reach into a space that has been explicitly removed, you can't expect everyone else to do so in exactly the same way you will.

          • flufluflufluffy 49 minutes ago
            The HTTP standard does not define a body for GET requests. Therefore, proxy implementations will typically only copy the data from the request header when sending it off to its next destination. They don’t technically “delete” anything. This saves compute (and possibly bandwidth, if the request happened to have a body, although the whole point is that one can safely assume a GET request does not have a body per the standard).
  • AtNightWeCode 49 minutes ago
    Kinda pointless since traffic is encrypted. If you can terminate TLS you can apply any rule based on the content as well. Like headers which is more reliable.
  • brookst 5 hours ago
    Wouldn’t just putting an etag on POST requests accomplish the same thing? If I’m understanding it the server has to maintain state to ensure idempotency.
    • CodesInChaos 5 hours ago
      QUERY is GET with a request body. So it must be safe, not just idempotent. Where safe means it has no significant side-effects. Typically servers will not keep any state for QUERY requests.

      There is one interesting variant though, which uses state: The client sends a QUERY containing the full query, and the server returns a url usable with GET with which this query can be triggered in the future. Similar to prepared statements in SQL databases.

      Using QUERY for GraphQL queries (not mutations) would be a good match. These only read data, but are sometimes bigger than the url length limit.

      • brookst 4 hours ago
        Thanks for the explanation!

        I still don’t get how idempotency can typically be ensured without state. It very much depends on data model and application design. Even side effects like using a user’s lookup quota need to be handled at a higher layer than HTTP (I think?).

        • wongarsu 4 hours ago
          Imagine a forum where comment ids are client-generated UUIDs, and comments are inserted with "ON CONFLICT IGNORE". Submitting the same comment twice would simply be a noop

          But what the Query method really targets are things like a graphql query that can be multiple kb for a single query, but only reads data. Sure, it might count against rate limits, trigger logs, etc. But at a conceptual level resubmitting the same query should give the same result (if the data didn't change). And since you are only reading data, resubmitting is safe

        • inigyou 3 hours ago
          Yes it varies. Using the QUERY method doesn't automatically mean your app is idempotent - it means the browser, and any intermediaries, can assume it's idempotent. So when you go forward and then back they're free to reissue the request and you won't get the "this may repeat whatever you just did" popup.

          If it's not actually idempotent but you're telling the browser it is, of course you may cause bugs. Same as GET.

          • CodesInChaos 2 hours ago
            I think PUT, which is idempotent, would still require the "repeat action" warning, since it will overwrite any changes that happened to the same resource in the mean time (unless used with `if-match` or similar). QUERY won't require such warnings because it's safe, not just idempotent.
        • Joker_vD 4 hours ago
          > I still don’t get how idempotency can typically be ensured without state.

          Well, how is "GET /index.html HTTP/1.1" made idempotent in practice without (additional) state?

        • CodesInChaos 4 hours ago
          Minor side-effects like quotas or request logging are generally ignored when considering the semantics of http methods. I don't see any complications for QUERY that don't already apply to GET. It just allows you to bypass the url length limit by putting the data in the body instead of the url itself.
          • uberex 3 hours ago
            Exactly. "GET / is idempotent" ... "But I just launched a DDOS against / and now it returns 502...
      • trollbridge 5 hours ago
        Ideally, libraries like FastAPI, etc. could be configured to translate QUERYs to GETs, until you can rewrite your code to automatically support both.
      • n_e 5 hours ago
        Interestingly, despite the QUERY request being safe, the RFC says it's subject to preflight requests:

        > A QUERY request from user agents implementing Cross-Origin Resource Sharing (CORS) will require a "preflight" request, as QUERY does not belong to the set of CORS-safelisted methods (see [FETCH]).

        • CodesInChaos 5 hours ago
          That paragraph merely describes how existing browsers behave, it doesn't specify how future browsers must behave. After all, a HTTP RFC isn't really the right place to specify browser specific behavior like CORS, that belongs in a W3C/WHATWG specification.
    • Joker_vD 5 hours ago

          Unlike POST, however, the method is explicitly safe and idempotent, allowing
          functions like caching and automatic retries to operate.
      
      Essentially, it's for things that are inherently safe/idempotent already (e.g. search or indeed, anything that you don't mind being retried) but require a lot of data passed in the request.
  • nottorp 4 hours ago
    It's as bookmarkable as a query with its parameters in the POST data...
  • geth101 2 hours ago
    Just allow body for get. Problem solved.
    • CodeWriter23 45 minutes ago
      Nah, you need the 405 Method Not Allowed to be returned by legacy systems and proxies along the way to your bleeding edge server rather than silently failing whilst dropping the params in the request body.
  • lanycrost 6 hours ago
    query strings always had size limit, seems this new type will solve it which will be really good.
  • drzaiusx11 4 hours ago
    I don't hate it. Covers all the bases: 1.1, 2, 3/quic and solves real problems: get query limitations vs body content & post-without-mutation. Yes there are preexisting workarounds, but they're non-obvious.
  • haeseong 5 hours ago
    QUERY has existed in spirit for nearly two decades as WebDAV's SEARCH method https://www.rfc-editor.org/rfc/rfc5323 and the thing that always killed it in practice was intermediaries. Plenty of proxies, WAFs, and load balancers either strip the body from methods they do not recognize or reject the request outright, so the guarantee that sending a body is safe evaporates the moment traffic crosses a middlebox you do not control. Until gateway and CDN support is real rather than just on paper, POST with a header marking the body as part of the cache key stays the pragmatic choice.