SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c971657c75ed92cab8970158f1d39389ae239d8a9976891e4af43a370369ac3a' 
  AND token = '8IkIT0HFMgTxAYFWVHNVVOP1Vz0qxvkMfNZxqu6qxJE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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