SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a44875bac91b8523f2707ccbd68f48979bd24b2bab2d0892e87c40ebcd81f506' 
  AND token = 'VxvXyFaSyNzC2cG2lrGDMg5tnFRMa3xgOL+qsDgwiAs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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