SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ce91d8a726ce3d920e73b273074077bc6ac5fce536b4098b804da9d844526da3' 
  AND token = '9jyFvZ9UPelggiTVox8VmIasuHw9qXYC/tqvPGb4pNU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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