SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a6977687475261049c3052189385e19ad375d748ce89f40b76989401593173d' 
  AND token = 'AwDd2ygWJo+w2FcQtkYo8ryrnuzhjKXFu7kYY69O8FY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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