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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b31ce920a4f6e181b47bd4cfd4bc2a52bd47bdeaf2c90c6bd706c30a91b679' 
  AND token = 'Uq0fz/KWreQtt99JMUw7WjfAx64aJEofN2Yd2+hSa0E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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