SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c98b48fd95821c3c693820ea146661fb36644ed78098963a270a5fd914625561' 
  AND token = 'xB9Gahn0ASxByBWUIXRcXb47bEDJ7nExhy5fV/2Smj8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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