SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac608dfd23d013ac1740241fcaecae7d0d7f5b933822f9fd4ce6c2904f914760' 
  AND token = 'zKGIdddaxebj85dfpKXUnvB1tvHToetj6IaiiiEQ8WE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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