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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '19f8cca2729d73cee8dafe03b0336913720b80b2dd1eeb0d353794bdf2ebe972' 
  AND token = 'LU2MYtmaZb9/Lp+nkLVdsJJ2Ov/3/wGHI3Kj6tFp3rA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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