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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4a1988b8d7ab538606d2cf5a66bd475538552449bcec7a3deed8bf7189da38c' 
  AND token = 'b/r3wAP+zE3TBQkSlAjdMrL5fbtnQl8P0uWruNtjiyA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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