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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '08d21d36df0d9b1ba7a4995231c19e6942e5731a96760a87e47ef6d6ed155a44' 
  AND token = 'uAJPiXTNr0fN9OSKu7AcZbCo4yE54qOLiXvQJm4ocqA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}