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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '34f95ae25b5cfe8f0873852d69c800afa775e89cfde0f2b61af3d3ff84074458' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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