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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56c99089a69dd56a47deb9e2312690ddf43e3e2708cc9bf37bce0cb6673ba78b' 
  AND token = '6ROfWyLjy/BwdqQwllkpY/+yxdjiMN9AJoSm5XuiryY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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