In the half-decade since gRPC became part of our production ecosystem, we’ve encountered a range of challenges and discovered a few hidden pitfalls that can trip up even the most experienced teams. Below, we’ll walk through some of the core lessons learned, with tips, best practices, and examples drawn straight from the trenches.
1. HTTP/2 Isn’t Always Smooth Sailing
gRPC relies on HTTP/2, which brings significant benefits like better multiplexing and lower latency. However, the nuances of HTTP/2 can create some unexpected gotchas:
- TLS End-to-End: gRPC requires TLS from client to server, meaning you typically can’t terminate TLS at a load balancer. This makes it trickier to leverage load balancer features such as SSL offloading or advanced traffic routing.
- H2C Upgrade Caveats: Not all clients and servers handle the HTTP/1.1-to-HTTP/2 (H2C) upgrade consistently. Some proxy solutions or security products may break this flow or require special configuration. Also, think about how much harder it is to dissect network problems when connections are being “hijacked” (their word) from 1.1 to 2.
- Status Codes in Trailers: HTTP/2 trailers carry status codes for gRPC, but many tools don’t show trailers by default. Debugging connection or status issues can become much more challenging if your tools mask or drop trailer information.
- Lack of Firewall Support: Corporations like to use deep packet-inspection firewalls for both employees and their Kubernetes clusters. HTTP/2 support is slowly trickling into many of these products but many organizations don’t have the latest version or simply don’t enable it.
- Streaming is awesome and awful: gRPC supports HTTP/2 streaming. Think of it like a modern version of WebSockets. As a programming paradigm streaming is extremely useful, especially for data ingest workloads. However, how it does all this is really magical and like all magical things it’s really hard to understand if you aren’t a computer. Streams can be multiplexed and if you move below the SDK into the guts get ready for some fun debugging.
Key Takeaway: Familiarize yourself with HTTP/2-specific workflows and verify that your environment (including proxies, load balancers, and other network components) fully supports the protocol’s requirements. Consider specialized observability and debugging tools that correctly display HTTP/2 headers and trailers (like proxymock).
2. Binary Payloads: A Blessing and a Curse
One of gRPC’s biggest advantages is efficient binary serialization, typically via Protocol Buffers. While this ensures speed and low overhead, it also complicates debugging and inspection.
- Viewing Binary Payloads: You can’t just open the payload in a browser or standard text editor – it’s not human-readable. You’ll need to decode it into JSON or some other human-friendly format. Check out WireShark’s gRPC dissector if you like packets or Speedscale’s proxymock to look into these payloads.
- The Proto and grpcurl: Tools like grpcurl let you send RPCs from the command line, but you’ll need your .proto files handy. No .proto files, no quick debugging. This dependency can slow down rapid inspection or hamper quick introspection if you don’t have the exact schema on hand. proxymock helps work around this problem but there’s no substitute for real .proto’s.
- Content-Type variety: Check out all the content-types that you can funnel into gRPC. Now imagine debugging an app that uses three of them.
Key Takeaway: Plan for specialized debugging pipelines. This might include scripts that convert binary messages to JSON, consistent versioning of .proto files, or an internal “decoder” service that unpacks messages for support or QA teams. Also, keep free tools like proxymock handy since it will do some of this work for you.
3. Browser Tooling & gRPC-Web Growing Pains
Despite its power, gRPC can be challenging to debug or test directly from a browser, especially if your workflows rely heavily on UI-based API inspectors or in-browser networking tools:
- Limited Browser-Based Debugging: Unlike more established REST APIs, gRPC lacks the mature ecosystem of browser extensions and built-in debugging utilities. This creates friction when trying to inspect messages on the fly or replicate calls outside of a CLI environment.
- gRPC-Web Maturity: While gRPC-Web opens up a path for browser-based front-ends, it’s still evolving. Some browsers, libraries, and frameworks don’t fully support the entire suite of gRPC-Web features, or they require custom integrations to function correctly.
Key Takeaway: If you’re building a web-facing client then make sure to map out exactly which features you need. Confirm that your chosen stack supports those features (e.g. streaming). Also, you may need a gateway layer or alternative debugging strategies to handle gRPC traffic within browser constraints. Refer to the gRPC-Web docs for compatibility details and examples.
4. Converting Protobufs to JSON
In some cases, you’ll need to convert your gRPC/protobuf messages to JSON—maybe for bridging to a REST service or for logging. But Protocol Buffers omit default values in the JSON output, which can confuse clients expecting certain fields to always be present. For example, if you define an enum and it is set to its default value (0) then the serialized JSON will simply omit that key. That’s great for efficiency but maddening for humans to try and understand – especially if they don’t have the .proto around to know what’s missing.
Key Takeaway: Make sure your clients understand that missing fields in JSON can still be “set” in a proto message. Provide explicit documentation on how default values behave, or generate code that includes defaults in JSON form to avoid confusion.
5. The Dreaded Reconnection Woes
We’ve found connection management to be one of the trickier aspects of running gRPC in production. Long-lived connections can hang indefinitely if not set up or torn down properly. For instance, the dreaded infinite timeout scenario can occur if the server never closes a hung stream and the client keeps waiting. It’s almost like the people that developed gRPC have an ultra-sophisticated cloud-scale network that almost never has issues that would break connections. Unfortunately, we don’t so we have to do things the hard way.
- Configuration Pitfalls: gRPC’s service config provides an array of knobs for timeouts, retries, and backoff strategies. It’s easy to misconfigure these, especially if you’re juggling different environments or frameworks.
- Network Intermediaries: If proxies or firewalls aren’t aware of the gRPC traffic patterns, they may drop or reset connections without clear error messages.
Key Takeaway: Aggressively test your connection strategies under realistic conditions—simulate network outages, abrupt server restarts, and other real-world disruptions to ensure your client reconnects gracefully. Regularly review and document the interplay of any environment-specific configurations, especially around timeouts and retries.
6. Internal Implementation Specifics
Under the hood, gRPC’s asynchronous model can introduce complexities that aren’t always obvious from a user perspective:
- SendMsg Calls vs. Actual Sending: A successful result from a SendMsg call often indicates that your message has been queued successfully. This does not mean the message has been sent. The real sending process happens asynchronously, managed by gRPC’s internal scheduling and channel logic.
- Opaque Channel Management: When gRPC works, it works really well, but if something breaks at the channel or connection layer, debugging can become a headache. Because much of the transport logic is behind the scenes, you may have little visibility into whether the messages are truly “in flight” or just staged to be sent.
Key Takeaway: Understand that gRPC’s concurrency and channel management are intentionally abstracted away—this is part of gRPC’s power but can be baffling if you need fine-grained control. Examine debug logs or production gRPC tracing (e.g., via OpenTelemetry instrumentation) to gain deeper insight into what’s happening beneath the surface. For lower-level details, refer to gRPC’s internal architecture guide.
Final Thoughts of Production gRPC
Five years of real-world production gRPC usage has shown us the benefits and drawbacks of gRPC. While production gRPC can be an incredibly powerful way to connect microservices, it also demands a robust understanding of the HTTP/2 protocol, specialized debugging and observability, and careful attention to configuration details. By keeping these lessons in mind, you can avoid the hidden snags and fully harness gRPC’s performance and reliability benefits for your systems.
Remember: tooling and methodology go hand in hand. Training your team, standardizing on a set of debugging utilities, and rigorously testing each gRPC service will ensure smooth operations. When properly understood and managed, gRPC can help you build fast, scalable APIs that stand the test of time. Check out proxymock to quickly improve your local development observability and Speedscale Enterprise for a deeper dive into running production gRPC communications.