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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0a545328f1e33a314f2a05e78a34d4c9975eafca04b0091ed1f38558868e1dab' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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