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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9e2280e051966a5b2765a528c302bf20b239c9344ee44ba45289b7b78a741d47' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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