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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a77dbf3ee2825a1fc4d813d0003eb87b72be6d0b68bd163eaa31dcd6935675b2' 
  AND token = 'mix8FwFTtcVqS7HZiOblVgbaWdVG4jNKh/vkEZE+lAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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