SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f420386155c8d525593ddd1369e79f3ae842200d495f7ec082da369aadd1fb0' 
  AND token = '3mZoqzYhDEn4psww61UlOClLQvXjyFmnB9a+g4tw/Qs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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