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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a83e7dddfde12ee408f19f048c5717b3418be9d3e72ca2baca02de4d0e030d15' 
  AND token = 'sgFw5lCjlv3c+Jdbk/JNHalEFSxBWUeXbDpwjxkt7Lc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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