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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '780aba2f89e4c7b0334744c9e290a30e1c3efff33c4a4ec9ae47fde54960e1f0' 
  AND token = 'i3Gn/tn+EjpRshw7Gfpqg3C9pDZcY9nGCs8joZ8FSXU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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