SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '876b6944c164bdd8f5e02bf35d11cfcf39c93ebfbfce624d4aaf1225ff944753' 
  AND token = 'JkSaXZNfCUCLWiaNwBqACanctl6rnPYhGBaFZf31AmA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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