SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '503d02015c959bb222312e322a57ea9b519930635d0af5e0bd8e0b17a17435d6' 
  AND token = 'iMBK96C2QYcy5CH524iJADXlZSUgeFTEpoq+gJuYxzY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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