SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b740646c573ac8227957a59d8320f51ce8f9f017769da090d3477d3cf0bca25' 
  AND token = '4gHptRN6JxNYiwgjtCLCdfm51RHmpHckKqQHB3AQzJw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}