SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe18fa96f350a8bc08b95592b72fc3a42fff779fc61529676308e77571853423' 
  AND token = 'NygJjUG8gazTXyvIfNDRDUkMIG1V+gVO35ugGJP0Lhw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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