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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39c305a3338949a4b25c3c9efe30b7a09993862de0e9ff1c7f5bc1abd1334bdc' 
  AND token = 'ZL8UnKfSmHrfbw4ENiuDQ+RT34+NDc5QZKJPhlJYb2s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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