SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3876c8853845761a004c4d908ff232f9dfd18a54ad774d66f5a5854713b50782' 
  AND token = 'bCU0PTJObmtpYgXOs8M5VXS7QRvbnOFf21Kzny5m8o4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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