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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3c99aed4eb1e24828f8fe07778ab20a5a8627ccfb2f4784e09e50ba56c68f3b' 
  AND token = '6rujuCxG9T8dB8AuhV/jzJGrO9oUe8aqFxcEiPGyZOQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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