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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e7a6fac7ecf8e728026896dbc9ed970a74e76400e85741f5c1c2d6add993c5' 
  AND token = 'Miy3jv2d1Tv+VLJDTSZhab7WH3ATMRPIV/GmUNiw/lM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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