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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '356922edc8d4987b38b6bc0fbb2245bb257df988de38d806ab4e593d0b0c6690' 
  AND token = 'JmquzhVs5UTiq4/88zUFeokrFXEfGgj13SLnruTtsaw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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