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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '51a845b270b8f1bd7914a3dd13b58f1a6fd2620d2b8b25a0ce25a60c4593a751' 
  AND token = 'Wpb5bWBJMRQBpenXvQVQKieXI1vfguMfQi6E0WYRhLY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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