SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a399e000717cef90553f0ff6269511e88841e1d9f6ff562314464237de39899' 
  AND token = 'vAnUbAtA6OnlnsyH1nnl4QR+LdU0kAhI8HmyD1+nVDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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