SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2a880f47c248575a2a5aabfaddb51bc6e8238dcf644985734d8636c2dcdc558' 
  AND token = 'RFlS/Kq5MACGLA0AUM/vS5LXXcWEVYI/qnJZHbuosCw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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