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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd9c3cf279dbb3a8ffb43761a393b8d44bf62d3d1549015629ed49b9f78784846' 
  AND token = '2v3Bylb9UdC6Df3mNTDfk59WT/cJ4BON+hIoSFrT/WY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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