SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '434f2b1f727208754e6fa1c5537570e909b7638bd31413eae4483c06a7c5f923' 
  AND token = '8jOPpOvRzEWYxFDeP4wYMbRC/olrPh692rV7b9aspxk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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