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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9976bd2d6b6c3960546cea7e0b841e426b1868f29a0bbd7f8d6606180611e0df' 
  AND token = 'UD0DzSCn2YAPwTbuwNjRlXhJogFToi8uVtQHomp6s4o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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