SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5021a838e91048d9975c19d1221435fd3be050311734141c9fcf5b391c24ae0b' 
  AND token = 'ucyXLx2GmFLLzO+JR1F3Nui6fj/Jdo8YFCbmm6GJFZs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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