SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21f6203fc6781fca4c92011cd2d5a85b486880d4dac17cdf1fee8a6cc98f6fd1' 
  AND token = '37f9h8JgGvcBcoJqBhrPOZH9KmjZ08eNz/X5mW+svF0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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