SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '978bd7c720d3b2f3f152296de0a25dbef65c68b9ff1037ec9d6033e94cb39943' 
  AND token = '6W3ZWVbmmo44XuhbhDznt7s9NqPLKwBhzzG0U5IDkyI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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