SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '503e989d0c06ce3b6c570af1086213911585a73355578bc1d6f2333120e1ec24' 
  AND token = 'EcoLjyUd6sotQTJJ6jBOvVVHRMZ1CfbqctBlqSimlVA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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