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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fc989bad8d7e8b0ad65c0e0792f05ba0ef94a4fedeb6f049f1796d7fae1cc05' 
  AND token = 'd+9HxvEOMUeUo24z+tRkkzauF9udmcDLFa/psLWImW0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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