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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3108ecdb6b0be572d9e72323013300248bf6dab2ad359e30e2c24e9f43adf4fa' 
  AND token = 'UWwjttQXl/h97kAhGKYUywY+VVl4nYjeWNQlhS4xBxI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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