SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f249c2acb3f2536b3ac20b644ca2aea9fe0cc18bde403e585cd3e671bac0dfd' 
  AND token = 'gnDCbSDKDRXZL0dVQqFnjAu8vk+XF7p+XfzoPYWH4sQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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