SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6c11a71bb83300577cb8eb94d407585fae0df53816125d63fead2b79baf49d6' 
  AND token = '+LSCN0irVMGn9PqHJ/WxqRchN2YSgQQx/s4e0JkmmXI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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