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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3f9caadf0b5225d72dbb1ba6ed3f1ea157c118b8f9ff4d41bcceaa46d13550c' 
  AND token = 'UkUA6JrZkXJVNNp5Qhm4tnZgiErFY51+fGWSqdkv4uM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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