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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9786a6d51b68eeee6cb4e9b39d2a359ab5bdd6cbfa0c236056b5300055ca611' 
  AND token = '0TKfFlvY3dp+1ugJqWEQ4yXzkHUN8few9pfpMLvNCKM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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