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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5d8f6e7105e1e141fe04a59d8ec8a304573699558ad5038b02a64e8fa26c8437' 
  AND token = 'S9sjgAg1tWIAN56fw6mBNbb1a1ImGP/7nvQg0ll0BR0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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