SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '92b21aef6d6754d81f9df89daafd703343b00e66663c5cdaefcc2c9d295cd266' 
  AND token = '4a3iiCVbL0DNPYA0fG8o2hYsfU0YhWsAHe7fetU/6wo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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