SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8fcb7dd9806e0e4fc03770ee261d4b07983d4d5b4ef9526e815d8bb4c2898d9' 
  AND token = 'DQpqT1jRqmUQGzVZDakM6VtR9gZzs3SFI/ZmTLxfJdY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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