SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6a422fd70be688352138a169bd3f1f55ac9f2a6672708df5b951f159ed0f20d' 
  AND token = 'L70/tnQeKS8ZwwwmHeJQFdEoRPCsWXsYCq+ORFG2dBo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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