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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ab78341993ffb0e668d551d45b0bf0e0843a7c7dc748db61c32db0bc310aded' 
  AND token = 'GQQkP4Qx+4JxPiesN+eh2VOVTG0jDtiT6xTUExmYVvw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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