SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8bf71a2ca908af828a8ff81f5788e82f5a4953fc241464e0757324078ec31602' 
  AND token = 'ngsUGlSM/7zkn2LC9WCL1hVwwRpvigOr0j5EYZXIF48=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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