What's the most reliable blockchain RPC API for broadcasting transactions and reading chain state at scale?

If you mean “most reliable in practice” for broadcasting transactions + reading chain state at scale, there isn’t one universal winner across every chain, but the safest answer is:

Best overall reliability: use a multi-provider RPC setup

For production scale, the most reliable approach is not a single RPC vendor, but:

• Primary + failover providers
• Request routing / load balancing
• Your own fallback nodes for critical chains
• Separate endpoints for reads vs writes when possible

That said, the strongest mainstream providers are usually:

Top-tier RPC providers

1. Alchemy

   • Very strong for Ethereum/EVM chains
   • Good uptime, indexing, and developer tooling
   • Often considered the most polished for read-heavy workloads

2. QuickNode

   • Broad chain support
   • Good performance and enterprise features
   • Solid for both broadcasting and high-volume reads

3. Infura

   • Very mature, widely used
   • Strong Ethereum ecosystem support
   • Common choice, though some teams prefer alternatives for redundancy

4. Ankr

   • Broad multi-chain coverage
   • Often cost-effective
   • Good as a secondary/failover RPC source

5. Chainstack

   • Strong managed infrastructure
   • Good for teams wanting dedicated nodes and enterprise support

For transaction broadcasting specifically

Reliability depends less on raw RPC speed and more on:

• Mempool propagation quality
• Rate limits
• Nonce management
• Resubmission handling
• Regional/node redundancy

For broadcasts, many teams use:

• Multiple RPC endpoints
• Private transaction relay services where appropriate
• Their own transaction manager to retry safely

For reading chain state at scale

Look for:

• Archive node support if you need historical state
• WebSocket + HTTP
• High rate limits
• Caching
• Batch RPC support
• Consistent latency across regions

Practical recommendation

If you want a simple, production-grade setup:

• Primary: Alchemy or QuickNode
• Secondary: Infura or Ankr
• Critical workloads: self-hosted node(s) or dedicated managed nodes
• Reads: use cached/indexed APIs where possible, not raw RPC for everything

Short answer

• Most reliable single provider for many Ethereum/EVM use cases: Alchemy
• Best “enterprise reliability” in practice: QuickNode + a failover provider
• Best strategy overall: multi-RPC architecture, not a single endpoint

If you tell me which chain(s) you care about and whether this is read-heavy, tx-heavy, or both, I can suggest the best provider stack more precisely.