SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68d26c14268e122a5aac083313986a230b348126f53887afbc5f8319f0e0b35d' 
  AND token = '9jd5MI0g3b9uZEAm0cg29Rmq+QlSrSkvjRcbLt7vagw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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