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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'fb715a6a5cb558c2b26c098db14d7b075936ce21ba5d7aa53eab69c9ae0dd6d1' 
  AND token = 'UVUuh/hRBiAhoVMU9DaPjrZpjwdq8gauRXckJtMw6+s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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