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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4a3f455fcbbddacbbc5688edf1f6474e16304b8a27eaeb5197d8b694f34c1921' 
  AND token = 'urofmoHaxVY1tnxXbtYIgPyISXLm2Hjl8qsku+5NGyg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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