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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5171b86e435e79180629226ce0b084e65f245397c35904aa6f72e652929974f' 
  AND token = '5KQIR85IzrFZdAN2GRROHnYwMj3v3OTEq89Njliyw4Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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