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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '350e479bc28e9870af9688109e7da23b7e7465acf787b52aef333767f7b2de21' 
  AND token = 'WU/aubfx/xnN8F+tGhxux7VEfiaPks5xT0W6S+5LCGg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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