SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5e975c9320b531fda13033029da5a141ac57b2b623f96389822f3c94dca9066b' 
  AND token = '4wLT3dLFuupEyDprKvJylLfmejVe11tSY5ZPoCJqEV4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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