SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b68a0e7128bc121c21fbc457cf00707ec7863c4073f6d725701194cae7782acf' 
  AND token = '1DhKvuGXD0wemrQAl27dPRgf+MkcD+/MnckrzeXg6e8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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