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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cdbe978d13683a2173e157331736c9c6b8795c4c19d02b7fe976b357f528bc8' 
  AND token = 'mQ4SEJ2PL5szQk+iiyuM5Z1KDUmLEs9hWzrLy7dKy+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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