SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cc931a41ffd1a130a62999fdca3725e30da89e1c7c262638f130081493de215b' 
  AND token = 'xjleS4DahtRj10P28SDjKXEkLGdjvmPFISAZq+w5qSw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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