SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55ef38979f97a8ec6b81fcb8bcf99fa91e432fc6405e14bb6d623a3808ebb37a' 
  AND token = '/lwJWkM1N1sYfn5LWV18Ny9oPRuucOvNPUBjXFmKKpg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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