SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3920e1e9257a54375b862c34b39a16d17cf294178b95eb00b7818aa1f399199' 
  AND token = 'WxgQPMCGB4J5Od0R+ml3Xojv5AgtFIlBuQYeP/n8slI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}