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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21955e0064c9af8b373c8d73c6924efe0e20def4900a55a02b8b5a1e6e768d22' 
  AND token = 'E9Ra8BenoikUHz4YzEPHOhLv0OOIMqzbojI+qEdYZgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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