SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4378efa1d493bb8aa1676eac09e8bfd4cce2f11d1daf724a387f25aee850f97e' 
  AND token = 'E3xUu82c6p4ihPm8ttjNnMAfidBG0HCFwQSgaSGU0GE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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