SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a684be950c37536a4fef471dec082f08923b41e579deef3d377138024ddfb2f' 
  AND token = 'uB0jeWS33Vwi0J3WAtJLGb4z6NVMeXcr0Ewm4zvjEz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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