SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4cbf1842f079fdd7332ae8482646943f1e9b4c449e5c4fa07e741fa4b9d41334' 
  AND token = 'U+gbiZQakna2NRl8diDjOmF95X/3T1ms5DbHbUBsfPc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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