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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '78c504d8e747722c7321a67c491bba5cdf5a6c2ce2bf0c1f4d05dcaf0c8a4620' 
  AND token = 'E6hMMYjQZKYxIFc/D5/ptXD6SlLQ/TtIByEibhBc3nU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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