SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '25abbbbfd41d0e3023f7b3556494cbcb88c12991143f28a4228d508bf57effcc' 
  AND token = 'R/6FEd8Zs5P5Jxp+5ZKeWKjkQf/UdgTn7xywv0oYwxk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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