In what cases is using REST unacceptable or inefficient?

REST API can be inefficient or unacceptable in the following cases:

• Requirements for low latency and high performance: REST uses HTTP, which adds overhead. For real-time systems or those with high speed requirements, protocols like gRPC or WebSocket are preferable.
• Bidirectional communication: REST is request-response and does not support push messages. For event-driven systems, WebSocket or MQTT are better options.
• Large volumes of data or streaming data: REST is not optimal for transmitting streams of data; specialized protocols are better.
• Security restrictions or network policies: In some corporate environments, HTTP requests may be blocked.
• Complex transactions: REST does not support transactions at the protocol level, which can be critical for some applications.

In such cases, alternatives like RPC, WebSocket, message brokers (Kafka, RabbitMQ), or specialized protocols should be considered.