SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f2c9445fe578d96f55de643daf7228b64ca2053282659aeb2e531437372247d' 
  AND token = 'jVtUfX6OFJr8bA7hu5afMwt8rLtPkPzKHOKOoiEZbMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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