SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '474371ed4fba74d530e1cb52ca542494d157f7981027962876b2c8c132d9a606' 
  AND token = '6Fq/kzFI8ZRXgTP848Kg8vVCX0rvfVncgwxbtjRD53c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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