SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e675a293a295953b5f149000c75cca6c507a2d1b8d97ee70b9f52db21343dfe0' 
  AND token = '0UfrPIHj3LUlfwtnqajNoh0kz6gRkp/DG6CZzbPntJc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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