SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8e387c3c682308ea311e118addb6748afff5dc51f12266e16c81a12f9542402' 
  AND token = 'WPQVy0Hfbpcv5M/jJ7Nb4ogmPhQ4K9nJHhvaQuwmpGo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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