SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8dcdd3564e6ed2eee192e56433d8ad2c45fd5c97f9462a8eb7f464865ac3942' 
  AND token = '6VnOA5i0dIlvBimE+ED343l8Yb9OM8fPLbsNMqYVzuM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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