SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ef30a62c6ea07b92eba40248623919dbea8c4edbf5a50a69965447abe9ad2bc' 
  AND token = 'LkWj+zjwQ0vIcHkbfbgKDWrCbvSkYgY5spkvhlPCbkc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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