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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ea0e5dee9b4773b356d4304d7c274526fd94cb09d9771f33b05315b1d5e96b45' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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