$ cat big.jsonl, | sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/,/g' | sed 's/n/,/' | sed 's/^/[/'| sed 's/$/]/' > big.json
This command converts JSONL to JSON. It takes about a second to convert 30 Mb file.
The first key point is to use JSON Lines for real-time data streaming like logs. Say, if you are streaming data over a socket (every line is a separate JSON and the most sockets have an API for reading lines).
Logstash and Docker store logs as JSON Lines.