SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e52aeacf5718bb833a1f99caca52c5798b0dbdd5fdd928629ea0f41ba597432' 
  AND token = 'pxZEHqz4wfgPGqh270nqznbNjKPLTXaDSqVyL21Ge6E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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