SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5c7c55228cfd5f4096f7c8c77a4e316875c588d1559f8aab3b0a518f664d8be' 
  AND token = '+PrBFiWIuRBxtxXjbXouYDgVzwXwhLbqeL5oh4Qoe4M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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