SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51fed22628b125b6d5e49f8d15f7b4105745ea78f19a51637b66de0303048a4e' 
  AND token = '9jGmEFDH9fURyXYZhQCUYkEynEDgKG6UnTYlwpSVwAg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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