SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '993d36040fee366fe522dd36fd1e4534e92078dca4bd1ff682d74a2e0f581ec6' 
  AND token = 'gcHwKOweYVIqY5/+SX/RttpxAwlWonzcKWVoak12gBQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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