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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9bc52146ecc584e5d60be5371c4180b3da934f5afcec6c7e4aa2e5b89ac66a5' 
  AND token = 't8516kBlYDdK91g/+BTR+1anqp8hIpgoqKqmHEV/t9M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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