SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b8421219766ca6677b5c060c43ce3c5fa6f8cd91694f598b3193f2e80837fb9' 
  AND token = 'mSBl+vLeCHqPHRDrlmt/f6YbLzvYVpLndwfM2Pz5VD8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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