SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b312845f60b9f718b0d40df02fdf60de1b1885b16485eee9f9b9c614d79d577c' 
  AND token = 't6LBGznYI47LHl6noGzZTzrnsA6o/WlHrYlpzNrEwcc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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