SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b9d620bc82e82a5cb574bb911fa83d120e8c556a4d3cb851719a86f71eb445' 
  AND token = 'FgkzLnfX6F9n7I/fKBmK1/+3stwVPwjY5XXyMfB2CT4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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