SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f728a2cd87a2473729693debbf989fa02e496fc6276c1d2225aabd6bedfff3b' 
  AND token = 'u6GDTCX/wyTsqhCfFDTijztOhX0qctU7huq3IH0AV+M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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