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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '751bc52ebff7c399f083760d12ad9cd851878aa68c052da0ad5dd1fe6ba8bd37' 
  AND token = 'JR/WwthOlLLO5lkTtesYPTmSKjYxrWhmuywC7xK6g6w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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