SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '871a189b388162abc370e038d71d6e5d59ef2f1b54219a57be03c5016bdf6791' 
  AND token = 'OJQoh1Qu+cbtq+TIblZzAG662lIK3qusMtJ/YXKODlE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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