SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6c747734e6ba217cdb443d03a7cd6d79040fa235f5af29929df8a3f28c59f5e5' 
  AND token = 'LxBNq7mK51qeKXgnJStzBtyk+VfKdzWpqsTxfYBZEs4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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