SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2c1695fa45f9ae7d00d54b21d6ae7213780081b4f50ca33c19222ac61f3b0a1' 
  AND token = 'b6ClRrIWe08TY7xtuGg/WzJFTGa00+wcT/qKXCVQVqI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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