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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'ef47c667fa11b7ca17083f9636e8e34724f0dc33d6653be0c471e8c5353e66f8' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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