SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5db739c2736b2907c09f996fede6e401f8a5c71def5a1350847cbd70e706f24' 
  AND token = '1fwwh6Fg7P45IzIqALZrfSG+pvJMe9VMtqZDmzOwFDc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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