SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f604739108e47f5dec5d29a20db61d32e129585e92b252362f7a296b492f5455' 
  AND token = 'eh4IJFZwxTm4AGIi7jwh2CI+dSpOxVHJ7O/FZD8BCW0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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