SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b10b18aa171e758142bbb51696892d7325558045d319502b9e19db229f38a306' 
  AND token = 'JgQRvGLNdiciDWe0np5gKeb9Elnv9BPRS5HBnlnJeDc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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