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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4d21f5bd6da3b2ea366dd5d40abda0a98a9a2b6c2fd476d5dbf6971603ed372f' 
  AND token = 'yep4XtflAKuvt7kkHozHn4PE4kVhKlS65Zoxq1HZ8tQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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