SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78d702c44e99018774a483cb16dca9df56130de0263e4063ff811aa383b706e5' 
  AND token = 'up9QbT8CXKKrsDle/SFgIwYLU/HWcLqenveBOzZxKMY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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