SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '58f4b352535bf09c4842004f02f5b145fc3238347b1791811a647c3f156d5609' 
  AND token = 'QlIfIoK6xeaJP+YObT8RbPJV5ixk8OiKgYehAgc+rLE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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