SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f15691b7d0db87ebb074a6217a4bffc1e5b1b48f68e11add7bf99134dc03ca7' 
  AND token = 'BmbIVlhY+oyllewgVe1FIgm+kxLcH+JqcSTZqkpAHQg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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