SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8e76e04b90580cb8754ef52f2c7b3cba5609974de86a528296149192cb86a76' 
  AND token = 'by7ijN9wV5iaLauJSJyOTHM3GYSmEXwGFz4dN/CBKT4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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