SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c21f188a12b37746a5f59f962413cb7aa9ce5eb7ea7703769a7138ef9518f695' 
  AND token = 'pLLlrf12JpBv/wdQD+hxR8hhJnQ/HxHi9tgyG5BunvA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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