SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '994b6bf2e014b85078764f9183ba1e7a6cd9168246ab6485f9a8437f63170566' 
  AND token = '8L3QWVMK/8TUelgqIpZ1ZH+fVrkpIhUd5JvWu7xADZo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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