Quick question: When was the last time you wondered if you’re using the best tool for querying or formatting your Microsoft Lists? If your answer is ‘every time I hit a performance bottleneck,’ you’re definitely not alone.
Today, we break down the real pros and cons of CAML, REST, and JSON formatting that every Power Platform professional should know before choosing a data strategy. Spoiler: The most obvious choice might not be the best one.
Why CAML Refuses to Die: The Hidden Power of Old-School Queries
Let’s be honest—CAML isn’t winning any popularity contests. But if you’ve ever seen someone suggest tossing it out because “REST does everything now,” there’s a good chance they haven’t run up against the specific corners of Microsoft Lists that still make CAML feel like the only grownup in the room. It’s like seeing a retired engineer hanging around the factory floor, outlasting every new hire. Most pros—especially folks new to Power Platform or SharePoint—just assume REST is supposed to be the replacement for everything legacy. In presentations, REST arrives dressed in a cloud-friendly suit. Documentation after 2018 barely mentions CAML except in a footnote. Teams default to REST endpoints. Power Automate connectors wave the REST API flag. Ask around in most Microsoft 365 circles, and you’ll probably hear that “nobody uses CAML anymore.”
But then, quietly, the old XML-based ranger pops up right where you need that one thing REST can barely do. We’ve all hit that point: You open a list, the UI is modern, the Teams app syncs fine, and then you try to pull a filtered report with multiple levels of AND/OR logic. You stack nested lookups, date filters, and a couple quirky calculated columns. Suddenly, REST throws up its hands and gives you either a generic timeout or an error that sends you down two dozen GitHub threads. Try expressing a query with eight different filters and some child-parent relationships. REST will let you write it, sure, but the JSON gets ugly fast—and performance drops like a rock.
Not long ago, I watched a Power Platform team migrate an old SharePoint workflow—years of business logic packed into classic designer flows—over to REST-based flows in Power Automate. On paper, it looked simple: swap out CAML for REST queries, update connections, and call it a modernization win. But on day one of testing, the migration choked on a batch operation pulling data from a list containing 75,000 items. With CAML, the old flow sliced off results in neat little pages, kicked out only the columns it needed, filtered everything server-side, and shipped back exactly what the automation required. The REST-based version, running nearly identical logic, ballooned in both response size and query time. And just for fun, it blasted past the 5,000-item list view threshold, which is always a favorite trouble ticket. Tech support spent a week flipping through REST documentation, only to end up re-enabling the CAML-based query for those edge cases.
Here’s what stands out about CAML: the way it lets you build queries with complex grouping and advanced filtering that REST, for all its flexibility, still finds clunky. CAML’s structure isn’t just XML for the sake of pain—it actually shapes the query so it can be parsed, executed, and optimized server-side. That’s code running in the SharePoint backend, not your browser or Power Automate client pulling tens of megabytes over the network. When you need to return only the rows that hit three different lookup values, don’t bring along every item in the list, and avoid blowing past thresholds, CAML can quietly make that happen. Try this—auto-approve a set of requests based on five nested business rules, filtering for calculated fields and workflow status, all without loading every entry. Most REST-based setups either throw you back more data than you need or require running extra filtering logic after-the-fact, burning up memory, flow time, and patience.
There’s even a well-known backend story in the SharePoint world about massive lists—the real beasts, with hundreds of thousands of rows—where administrators had to script administrative reports. The rumors say that when REST API built the same report, it spun for minutes. Switch back to CAML, and suddenly the data spilled out in seconds. The magic? CAML’s XML is tailor-made for SharePoint’s indexing engine. The query goes straight into crawled indexes, skips rows that don’t fit, and doesn’t waste time serializing the entire dataset in JSON for the client to filter.
It’s not just urban legend or stubborn admins refusing to learn new tricks, either. Microsoft’s own documentation—usually quick to point out “modern” options—still quietly signals that CAML queries are the answer for certain types of intricate filters. Community threads from the last year have people swapping code samples for using CAML inside custom PowerShell scripts or complex approval workflows because it simply outperforms the alternatives in more than a few situations.
So is betting on CAML smart, or are you just risking future headaches clinging to something scheduled for demolition? The real answer is sneakier: CAML isn’t dead weight, and when you’re staring down advanced filters or those thorny performance edge cases, it consistently pulls its weight, sometimes better than anything REST can offer. You might even call it a secret weapon reserved for those frustrating moments when modern tools suddenly lose their shine.
Which raises a bigger question. With so much power hiding in CAML, why does every vendor, every Microsoft roadmap, and most Power Platform solutions still keep steering us toward REST APIs? If the old way works so well behind the scenes, what’s really driving the shift? Let’s see what’s waiting on the other side.
REST APIs: The Double-Edged Sword of Modern List Access
Let’s talk REST APIs—the darling of modern development in the Microsoft Lists world. It’s hard to miss how every new integration, extension, or Power Automate connector leans into REST. This is the playbook: Microsoft wants tools to work across the cloud, in browsers, with Teams, and on mobile, so the REST endpoints are everywhere you look. Need to plug your list data straight into Power BI for a quick dashboard? REST endpoint. Got a third-party tool promising smarter notifications or advanced reports? Odds are, they’re hitting the REST API as their gateway into the data layer. Even for developers, REST feels like a friendly handshake—everything works in HTTP, the docs are packed with JSON samples, and most programming environments already know how to speak the language.
There’s a reason third parties default here. REST works almost everywhere with minimal fuss. Whether you’re connecting old-school SharePoint sites or shiny new Microsoft Lists spun up through the cloud, the REST API surface is broad enough to cover most use cases. From a cloud readiness standpoint, it’s gold. No obscure XML to chase, just well-documented endpoints and parameters, ready to slot into low-code, pro-code, or even a quick script someone hacks together before a meeting. Modern app architecture almost demands this kind of flexibility, and Microsoft’s whole SaaS ecosystem is built to support it.
But under that surface, things get complicated fast. REST’s catch-all approach makes it easy for first-timers to ignore some real pain points until it’s too late. One of the first headaches is API throttling. REST’s openness means that, when your solution gets busy—or if a connector or script starts firing off hundreds of requests in a short window—SharePoint or Microsoft Lists throttle your traffic. It’s not always obvious when it’s happening, either. Sometimes, you get a helpful “429” error. Other times, queries just slow down or silently fail, stalling automations and user actions. Now add in service limits—thresholds on how much data you can return, how many items per call, and max concurrent requests—and you realize REST gives you flexibility but not always predictability.
That scales right into performance during bulk data operations. In testing, REST feels slick. Spin up a list, send a query or two, it works. But production is a different animal. Picture a workflow that breezes through functional testing—200 items in a dev list, everything smooth. Then the thing goes live, and the real production list has 40,000 records. Overnight, Power Automate starts spitting out failures, flows get stuck retries, and the support mailbox lights up. The team quickly traces the failures to throttled REST calls. It’s not that your script was wrong; it’s just that REST doesn’t handle sudden volume spikes with much grace, especially when someone is looping through responses or chunking up write operations. Even a simple “bulk update” script turns unruly when each call takes longer and the system shoves back with a throttle warning.
REST’s writing operations, too, can become a labyrinth when scale rears its head. Sending a few updates that pass in a basic JSON payload hits no snags, but batch writes? Multiple item updates using REST need careful orchestration—multiple requests, careful attention to concurrency, and error handling that can retry once throttling kicks in. CAML, for all its syntax woes, let you slice and dice server-side, submit a query built for SharePoint’s internal engine, and get exactly the result set you wanted with less client effort. With REST, you’re often left piecing together results on the client side, combining partial responses, and spending more time marshalling data in browser memory or inside cloud flows.
That’s the real tradeoff here: REST shifts more processing to the client. So now, instead of SharePoint quietly handling filtering, paging, or joining list data server-side, you’re sending a raw list of items back to your automation or script, then filtering, joining, or formatting after the fact. For some solutions, that’s fine—especially when you want to tap into Power Automate, Teams, or even third-party connectors that only understand the REST interface. In fact, for bringing data into a Teams tab or pulling quick updates into an app, REST is what makes it all possible. It’s also WHY you almost never see native connectors or prebuilt integrations using CAML—it would mean rebuilding that server-side parsing logic everywhere.
But that gain in versatility has sharp edges. REST works well for breadth—lots of integrations, lots of basic CRUD operations—but its reliability and efficiency drop as your use case grows in complexity or scale. Experienced admins and architects know that when you hit throttling, or permissions cave in due to badly configured app registrations, your automations can break without warning and the root cause isn’t always obvious. Troubleshooting becomes a process of sifting through logs, watching retry behavior, and praying the next release doesn’t tighten limits even further.
So, is REST the modern hero it pretends to be, or just a handy shortcut with some hidden tradeoffs? From where we sit, REST is the default because it’s easy and everywhere, not always because it’s best for every scenario. Lean on REST, but don’t let its convenience fool you into skipping a scale test or missing how much work you’re dumping on the client. In the wrong situation, REST is a recipe for performance surprises, failures at scale, and headaches for whoever maintains your flows once you’re off to the next project.
But if both CAML and REST have these uncomfortable blind spots, it begs the question: Where does JSON formatting fit? For many teams, it looks like pure UI sugar, but things beneath the surface can get trickier than the format’s simplicity suggests.
JSON Formatting: Custom UI or Unseen Trap?
JSON formatting is that feature everyone shows off at Microsoft Lists demos—take a plain list, sprinkle in some curly braces, and suddenly you’ve got a dashboard with bold colors, fancy icons, and even clickable buttons. All of this, and you never have to open Visual Studio or write a single backend flow. It’s the kind of thing business users and power users both love, because it promises instant results—no waiting on a dev team, no approval for custom code. Change a line, hit save, and the list view transforms before your eyes.
For a lot of organizations, this feels like magic. You want to highlight overdue tasks? A few lines of JSON and overdue items glow red. Need to add a progress bar to every project row? That’s a web search and a quick copy-paste away. Power Platform folks can build out what look like mini-apps—complete with conditional formatting, tooltips, and icons to nudge users in the right direction, all without ever writing a full-blown application. You end up with a workspace that’s actually pleasant to use. No more pleading with admins for a custom SharePoint solution or trying to wrangle a third-party UI add-in. It’s hard not to like a tool that promises results before lunch.
But the shine wears off once you try to push the format past its comfort zone. Here’s where the friction starts: complex conditional logic might sound easy enough, but once you’ve got six different states, nested if-elses, and a few calculations, the JSON gets unreadable. Maintenance becomes a real headache, especially when nobody documents what all those lines actually mean. Tweaking a color or updating a condition forces you to hunt through hundreds of brackets, just hoping you don’t break the whole thing. If you’ve ever inherited a list where someone “just made the formatting prettier,” you know how quickly it spirals into copy-paste spaghetti.
Performance is another silent killer. With smaller lists, the browser barely notices, and everything feels instant. Scale things up—say, that same list hits 10,000 items—and suddenly, nobody is smiling. I worked with a finance team that built a fantastic dashboard, tracking status and targets for thousands of projects. The UI was slick in testing, but after a year, when the item count shot up, users started complaining about their browsers crawling. The culprit wasn’t the list or the network—it was the JSON view formatting, layering extra DOM updates and client rendering on every item. The browser had to process every conditional format, every icon, every change, as the list loaded. A few seconds here turns into a slog when multiplied across thousands of records. Heavy JSON customization, especially when piling on nested logic or media, builds up page weight fast. Microsoft doesn’t publish hard limits, but the experience makes it obvious. You might not see outright failures, but users notice every lag.
All of this ties back to where JSON runs—squarely in the browser. There’s no server-side processing when you add or tweak formatting. Every calculation, every color choice, every visual cue happens on the client. That means network speed, browser performance, and even device age become factors in how usable your list actually feels. Compare that to CAML handling advanced filters or REST moving data in bulk—those operations use Microsoft’s backend strength. JSON formatting, though, bets everything on the user’s device, and there’s zero “offload” when the configuration gets ambitious.
And it’s not just performance worries. JSON formatting is still a moving target. Microsoft keeps tweaking property support, sometimes launching new view features quietly and occasionally making changes that break “creative” formatting solutions. Property support isn’t fully documented, so you might discover a trick that works perfectly today, only for it to stop after the next platform update. That’s one reason sysadmins tend to distrust lists that rely on heavy formatting for key processes—something as simple as a field change can unravel months of UI tweaks.
On security, JSON formatting is a strange beast. Since it operates client-side, it only exposes data already permitted by the current user’s access. You can’t magically surface restricted columns—the underlying data model enforces those rules. Compared to REST, which can be called from other apps or exposed via open endpoints, or CAML which is parsed on the server, JSON formatting is less risky for leaks but can still reveal more data if admins slap on formatting against columns users shouldn’t really see in a certain view. There’s also the temptation to “hide” data with view tricks, when what really needs fixing are the permissions behind the scenes.
That said, real-world lists often need fast solutions. Maybe the business wants a high-priority board with colored categories and quick links, and nobody’s signing off on a week-long custom dev sprint. JSON formatting is perfect for quick wins, even if it’s not the answer forever. There are scenarios—quick status boards, team dashboards, one-off event lists—where the ability to shape the UI in minutes beats concerns over long-term maintainability.
So, you get power, but at a price. JSON formatting can create beautiful, functional dashboards in no time, but it’s not the answer for lists that need to scale or stand the test of SharePoint’s shifting feature set. If you’ve ever wondered, when should you reach for CAML, REST, or JSON? It all comes down to understanding how each tool matches your actual needs, especially once everyone has moved on to the next must-have app.
Choosing Wisely: The Real Impact of Your Data Source Decision
If you’ve ever raced to finish a Power Automate project on a tight deadline, chances are you chose whichever method felt fastest—maybe REST because it’s what everybody’s using, or JSON formatting because the customer wanted a quick UI facelift. It’s how most real-world Microsoft Lists solutions get built. No team schedules an architectural summit just to pick between CAML, REST, or JSON. There’s pressure, there’s a backlog, someone wants results, and the default wins. Living by the “just ship it” mindset saves time at the start. The trouble is, you don’t always see the impact until something fails under load, a compliance check kicks in, or that simple enhancement request demands a full rewrite. The stakes start to show up after the fact, when operations slow to a crawl, an integration breaks, or data lands in the wrong hands.
The shortcut, of course, is tempting. You add a JSON view to dress up a list, or you hook up Power Automate with REST for instant flows. Nobody is hunting for gotchas when a fix needs to deploy “by Friday.” But what gets missed are the real risks lurking behind the easy wins—breaking changes as Microsoft moves the goalposts, server load that quietly breaks thresholds, or security gaps nobody sees coming. I’ve seen security audits catch sensitive columns leaking through a hasty JSON view left over from testing. In one case, a team added column formatting to make it easy for managers to spotlight “private” feedback fields—fields that, if you knew the right URL trick, revealed more than they realized. A few months later, compliance flagged it in a periodic access review because the formatting surfaced metadata that users weren’t supposed to see together. Not a one-off, either; the risk is real, especially when view logic changes faster than permissions get reviewed.
REST brings its own flavor of trouble. In theory, it’s all automated, repeatable, and built for scale. But it also means you’re now at the mercy of throttling, evolving API behaviors, and just plain silent failures. I watched a retail deployment collapse after a busy holiday for a very simple reason—REST calls that failed due to throttling, but only when the production list got big. In test environments, there’s plenty of breathing room, requests glide through. Go live, spike the volume, and REST quietly drops updates or starts retrying in the background. The flow looked fine—until you drilled into logs and found items stuck in a processing loop, simply because the API was protecting itself. From a business point of view, this looked like operations falling behind. From a tech perspective, nobody wants a solution where the only symptom of failure is a missed SLA and a queue full of “successful” but unprocessed items.
Then there’s the joy of maintainability—or, more often, the lack of it. CAML, if you’ve ever read an advanced query, looks like a history lesson in verbose XML. The syntax is detailed, and the documentation reads like a puzzle. Try giving a complex CAML snippet to someone new on the team, and watch how long it takes before they ask if there’s an easier way. On the flip side, REST endpoints sprawl out fast. A single solution might call half a dozen different endpoints, with each flow, each connector, and each automation owning a little piece of the API landscape. If you need to refactor or unlock a new scenario, you’re tracing requests and permissions across multiple moving parts. JSON? JSON brings its own brand of chaos. Formatting rules stack on formatting rules. After a few months, the pretty board becomes a minefield of conditional logic you can’t untangle without breaking features. It’s readable if you wrote it. Otherwise, it’s just noise.
Security is the other elephant in the room. CAML lives on the server side and only returns what the query allows. REST APIs go through their own permission checks, but endpoint sprawl means mistakes can slip in—suddenly, a script exposes data in another system. JSON formatting leans on whatever the current user can see, but masking data with formatting isn’t the same as truly restricting it. And the underlying permissions model, especially in SharePoint-backed lists, can drift when lists grow or columns repurpose. Keeping up with what’s exposed and where is technical debt waiting to multiply.
Performance, too, demands careful thought. Large, complex CAML queries can crush a server if misconfigured but can also save bandwidth by doing all the heavy lifting in the backend. REST, with all its flexibility, throws most of the burden onto network traffic and the client. It’s perfect for micro-services and cloud connectors, but at scale, the payload ballooning tends to punish anyone sitting behind a slow connection. JSON formatting, meanwhile, lives and dies by the browser: small lists fly, big lists grind. That’s before you start counting the cost of heavy formatting and client-side rendering.
Every method asks you to weigh those risks. Do you want maintainability, or raw speed? Are you building something quick to solve today’s problem, or is this solution likely to be here—and need support—twelve months from now? No single approach is perfect, and Microsoft’s own guidance boils down to matching the tool to the task. CAML in server-heavy querying, REST when interoperability matters, JSON for rapid UI tweaks—each has a sweet spot if you’re willing to accept the trade-offs.
Next time you’re starting a Lists project, ask yourself who’s using it, how long it needs to last, and whether you’ll have to defend it in a security review. The best architecture is the one that avoids surprises six months after you’ve lost interest and moved on.
Conclusion
If you’ve worked with Microsoft Lists, you know the most obvious choice isn’t always right. The quick answer today can become a headache down the line, especially when team size, compliance, or business needs shift. Before launching your next solution, take a step back and ask yourself—not just if it works, but if it lasts, protects your data, and makes sense six months from now. I’d love to hear your stories too. Drop your strangest CAML queries, REST frustrations, or creative JSON hacks down below. Someone’s oddball workaround today could be another admin’s lifesaver tomorrow.
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