SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '421f4a15a2bb79d8806ddd3905d5f6aa05d973ac7ea637e6f1646a42f56a49e5' 
  AND token = 'gvTx4YdmoQSYSMkG6iVv3/P+DF+fh0zP0ZPH7rlj0oA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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