SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3131d6ddf6261684a8c070bf5f8f398a1fb225f8b4063c5cd7ec5c580993487c' 
  AND token = 'D1+7hzyVtOrXZ/xLVtaXrYoEVoiwG1FUIyMDYLa2Dgc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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