SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1a2c84e5a92f0d65fbd00d7010865ffaf8a7964fdd12f881bf6752ea561df676' 
  AND token = '5a4JFcmxlhKZS3AJi+YIBOcldkNfrTc9sYMStk7PszY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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