SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81535f79713fd83a00863b9d581b5b0c1c281a9c2f849e9086efb46c2a38c637' 
  AND token = 'YvYTazE5kVBuRMpGUqBPHR6lZ7s7TtoQbTziYw845QM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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