SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7a1fdf6250132a893e64dfc1af344268ff977df6bc1aad9e4158f8e4952dbc9' 
  AND token = 'yLQ3yhJA2ppcpZ0INqLVmmv6PsQTNzOUwxXGYDplMDQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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