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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df3f9a78c0751f8c0e34ca7c115dff8a3c3aa193f0d7ec8981a3387439e2c6d4' 
  AND token = '6ZvGYkP27fi6Dc6z5K8wkFDw2Si0zKUI5ci8+Vnbcs8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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