SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b96946556b1bfc0e21d0c3992c1d3b50d296f0fa4d2a50d07920c577af71507' 
  AND token = '78qhEwiHbfz3reC8g87933iH2tlFyVwmqeKOS5aODMg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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