SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a61573eb5035f6c08ce3f19a3f20d99a29abd1b302ddc9bb4dbd7898f6c75d46' 
  AND token = 'QGs/36/uqf/JEiGSSCph59BBjFEEgHOIiF7oVMJ6AWc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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