SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '721cd13a293692a30ed16e999234c601028b03ef6f8abbd2b2facd95d4ac1520' 
  AND token = '49mtGrUJVNCp3h8I1ApoOAuuoBTpoHYltzOHHdT3zFo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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