SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4670a39c7159e01f29a513818716904fcb4372036994eac4a292329439b50927' 
  AND token = 'K2u36/Feg2z+8ytIbXe5IwvhxHgNGR6EEhI9eIFysUc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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