SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '398d543fa2bd75d74b9d75feb509f0f9eab96c176603e52d14e06f194c2d5c82' 
  AND token = 'uVJ3I2H4vZoYEie+BKy2EaBupZ4Z06/jLdlS1Ak3FFg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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