SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75ee7976045ce5fcf370525d4d77010aef609909d7cdb5346d4002637d21406c' 
  AND token = '9YlPoC2rG7X1JFuQxQOTiMU+4TqVXiSKxsWceKvPBY8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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