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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc6c9a00f0e3015b43c8f5453e7a4b45dfe4ea36c5ce9c059b5fe52b05f79244' 
  AND token = '6sqMItLeYtcm+ooXAvt7h5H+cWO1BKDEvjOUYG+rr8Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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