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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9847699d0f93bfa86830b0a399eb7096b224501fe52d6a49e6eaadd29a272b3c' 
  AND token = 'DSprB5dmFXE8fb8SgDxGQnuTEzlKjcM2LUJdDMIq1E4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}