SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3dbe7a75e8badaf54c52f1def74290ebf050fda42ba59c81842f6adb385ba71' 
  AND token = 'Z8xB1OjORkE0ohfwSmoJiulfpApOYrR+aDSbuDdBLeI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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