SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20b3bc6ec40d0f94493e42315a9ff76c396d5051a020bba1193e7f51f16fbcc4' 
  AND token = 'SvU/DyFbB/qM51yEw6GmHw09ccO6T6nZAbfuxY4blAg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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