SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a6f5eef81899fc73259812eac139b144b10bade88ba07f4d977f9b54a6ad138' 
  AND token = 'rKUGtgJV4eihJoInT+IOYY/U7UG1KMyv/d8Toza2ixY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}