SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7704ad315dd30f75d1a492dccda9a387018c19d28e6eefb07eae83933bcd018f' 
  AND token = 'zR0Rwj8a3nJy2gXqZF28tvFIlgiUHd0jIBjCfzmZmvo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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