SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '291848a9b0c6d64a5c02cabd612ad2bcb4919de122b7032d1a096574914725bc' 
  AND token = 'UG7JNxU4SuZcUaFQtZEgsAxZBQaBQ58AlyYu+F75M1s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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