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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b542e3f3fdd81b81311e75903ad314b2eff9fc7605ab6584c8be488a48aba6d7' 
  AND token = '71EUuF+LE+LOE8j5ZCgKHnxeQP4NPIDefdDaNpUikLY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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