SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9798ee1871994875935dd9811696dba8b0fce39ede1db12f902d9ac0dfa9571' 
  AND token = 'WCy058YkWe49W6yrCcBPggcJ3SEyYS6uJ2mXP/wddDY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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