SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd0956f324828201260d1740fab645bd152531210d419fe17cfef5bc4080ec621' 
  AND token = 'JQLUCJM9cimo8NtpPamMwpwUUyPekGiWq2cwvqzXHIo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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