SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1521a2837e03f143fb725a59857e44edaec4dc4cfe7331ca95e7902d9ca21c48' 
  AND token = 'eJddcTr77doXq+G0MNcGusDjywqcmH39OR35amFxbXE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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