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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ad712354e7f4abe5936d4561216515bb3032165050673f579a5385f91ff9099e' 
  AND token = 'f86L2kYc1sLpz6mt+U6D2kFh6o2ffODT7D3+eXcclsE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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