SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e3c1c16b28db803cb32bd25d32717dfbab1601f06ee3fb0194196a9d0b17b53' 
  AND token = 'lKUr8Qws3WsLNJjdBvqSmB0UrFKVyZy6H6Jio98RpIA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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