SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b75a9250d5b30e5e4901ea3add1475a05fc20ffe83855dd73d778451c00cd911' 
  AND token = 'sw85MWp3RMhDTAmfJ5+HhtGGZajG0afBeAslCmCiBCI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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