SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7e4d7566e32204f8829ec8411aebec945cbb2119873740202fbf45897a9081f' 
  AND token = 'oulI9tHfZInoQEuMNH4OwblEVxRiAe8WUA52SmUCWEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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