SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c439b54c956863832374aacee564ff2d3fffbf9a655a528c4b598786e72ef077' 
  AND token = 'bx92j5PLKST7BsY8dPRrKsYLeOiOGwb+IjCZXGUv0IM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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