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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b1c0da03702c9a8c721b48351ab870339b73c52a0ac9ffa612188ad2125bf12' 
  AND token = '7RCO438qQb10ddL6YV38rn7SrEJGL+reS4kYnUGcATg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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