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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c8cb35b53b6cca13a884840bcc1f01f66a12bdc66db01ebf1b19b0032fb953c5' 
  AND token = 'RMchkWKM5qmaDJVs5tzfNEel2Zwl4x9pp1vPTpEGtP0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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