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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a998474785dbe535fa6a1e1a69a743358c4df38dab79724de1ee6327284e2a58' 
  AND token = 'HcSRmmEPW2e1dlNmARj3rHV+0lXFpnP/0ziAwjAzrKA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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