SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b89a20dcab011685282f59110404c4c0d643d2d1a3c3f6b79b2c7604aded650' 
  AND token = 'wmjkRjFU+QQNfVwYoHOzNodO53lFAyQD/nUjXv7Uwzo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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