SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2733e176ffc4491f826e62371ecc61c8d557f54f57eab585076eade03113016d' 
  AND token = 'oRknU+S1NB3j26DaoQueLfSi+yLSD0fDIt3F/JYToSA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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