SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0d18d4568fada509b0e290638d0a8a1a9206abf373e542ed942f3b5e47821a17' 
  AND token = '6igBcQvskJoCgksvKReMoyS8MQQKufEgm5R0EXaQrlc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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