SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b87d3fc6bda09e7295aa6042810ae2b25244125765ba9e9886fe7d6aa688fee0' 
  AND token = 'KJ7i1jCYsHLQ9GD1yCAM+XQj9LW5pEMSajL4cHyfS38=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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