SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b71a87549d023060636aaeec7aa683b909e317668a4a13d3dc578161963e252' 
  AND token = 'LtIcngxdQjgk4EEwzzFrAmDwwK/OxTUcsAKxq+syFZ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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