SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21f5420344ba296bec105ab25e99cf1cd98395e00d6800814e4ae397896b4c1c' 
  AND token = '2yPilf+nuQuKoVPbTCeTyxNuw+CU75ivFdKLtzDmtsk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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