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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd21a75ad4ffa52c3bd253e1037e3ec3a0b4b512b4474bf240afe30b9f2d59a11' 
  AND token = 'saP1u59LSzqGOkDFA2JNoyGI+yIr5fuEWN8eSlHkEk4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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