SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b824c120a09259f1c1f115c08001696fbfc4178018f08b99e6fbaee6134ddb7c' 
  AND token = 'f6YHwtK+zuZ8kh8+fH/AMbM/15/BhXABQQNwGJKfBCs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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