SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd5904c58768c69a91b9e57282fd89462710602be2395e59f433c6a925ae322f6' 
  AND token = 'uU/lsJjyqf1NFoEPUGU2VIQ0C+jKXmNfy8POpGHY49g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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