SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35a730bf76edb90fee0946265d0af4006401767f3659b24cdb52b5d759f44582' 
  AND token = 'tSUx4RiGWQO1L3r94MBGZS3+ixwKzWsAW1NsU3mur4I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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