SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2670be6674d73ebf8ce5b54423ebc1caf0d7b78e1035c98f6ad3b653e15a8c8' 
  AND token = '5CzLC8YzONHmZQuoxFZqaZJz+1EJjCF9J7KVeHmG9ww=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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