SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '263d553240876befac061086bd90bd14ce855e57805f2af77dd72fcab288c2e4' 
  AND token = '9rZVskklG4OL63KBxF8+EovV+3VU9ai/IDPcv//qbL4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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