SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8997ecc0ddd0e7dcbb9bac82567a7f341459d1e3fee8a5fa7187ab575f39877' 
  AND token = '2W2rsDM95nVx0oK8w2XZ46knQj0PFREf+M/OoaMjHFM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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